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It is hardly surprising to know that the number of fatalities increase as the number of fatal crashes increase. What is surprising, however, is that there is a very predictable mathematical relationship between the number of fatal crashes and the number of fatalities. The available fatalities data for the states of Iowa, Kansas, Texas, and Montana have been analyzed to show that increasing or decreasing the speed limits does not seem to have any statistically significant effect. Nonetheless, other important factors must be taken into account before we increase speed limits in various states, notably Texas, which will soon have the highest posted speed limit in the US and the second highest in the world.
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Table of Contents
Page No.
Abstract …………………………………………………………………… 3
Introduction ………………………………………………………………. 5
Texas Proofing of vehicles ……………………………………………… 6
1940-49 War Speed Limit ………………………………………………… 10
Data available for scientific analysis …………………………………… 11
Iowa motor vehicle fatalities data ………………………………………. 16
The Montana no speed limit safety paradox ………………………….. 28
The Texas Interstate traffic fatalities-crashes …………………………. 38
Iowa statewide crash data and changing speed limits ……………….. 40
Kansas speeding related crashes-fatalities ……………………………. 45
Summary and Conclusions ………………………………………………. 50
Appendix 1: Legendre‟s Best-fit line and Einstein‟s Work function…... 54
Appendix 2 : NHTSA Workshop on Vehicle Mass-Safety……………… 57
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Abstract
Several state legislatures in the US, notably Texas, have recently voted to
increase the legal speed limits on their highways. Texas would soon have
the highest posted speed limit of 85 mph (136 kmph) in the nation and the
second highest in the world. In this context it is important to understand,
dispassionately without any socio-political and economic prejudices, the
effect of increased speed limits on traffic-related fatalities. Nearly 40,000
people die in traffic-related accidents each year, the social costs of which
cannot be overlooked.
A review of the fatalities data, or the fatality rate data (based on VMT, the
Vehicle Miles Traveled) often yield conflicting signals, depending on how
the data is “mined” and/or interpreted. Some states indicate increased
fatalities with increasing speed limits while others indicate just the opposite.
Indeed, according to NHTSA, the absolute number of fatalities has reached
a historical low in 2010 since 1949. Many statewide data reveal similar
historical lows. (The current depressed state of the US economy may
certainly be a factor here!) The fatality rates, based on VMT, have also
been decreasing year after year. Yet, there can be no doubt that crashes
occurring at higher and higher speeds, which are inevitable if the legal
speed limits are raised, will be increasingly gruesome and the US might
indeed witness an “epidemic” of traffic related deaths, as in the 1950s and
1960s, which prompted congressional hearings and historic traffic safety
legislations. Teenagers and inexperienced drivers are, perhaps, the most
susceptible.
Attention is therefore called to a new, and remarkably simple, method of
addressing this issue, as discussed here, which is based on an analysis of
well documented data on fatal crashes and fatalities in various states. It is
shown that as the number of fatal crashes, x, increases the number of
fatalities, y, increases following a simple linear law y = hx + c (see Figures
2, 11, and 13 and sidebar on page 15). The numerical values of the
constants h and c can be deduced using the classical statistical method
known as linear regression analysis. A graphical representation of the data,
IoKsMTxStudy Page 4 of 60
with observations made over several years that span different speed limits,
suggest no statistically significant effect of the speed limit (see, in
particular, Figures 14 to 16).
Nonetheless, the physical effects of an increase in the absolute speed
limits cannot be overlooked and the increasing amounts of energy that
must be absorbed in crashes occurring at higher and higher speeds (see
Figure 1) must be factored into any societal consensus on this important
problem that should engage our national attention – like any other major
newsworthy tragedy. The interaction of speed, safety, vehicle mass, fuel
economy and crashworthiness, and other social costs, such as insurance
and medical costs, will ultimately govern the course of vehicle
development. Innovations in materials technology, that permit the use of
highstrength, lightweight materials, might help us “Texas Proof” our
vehicles and spur a new era in high speed personal and public
transportation.
A review of the historical trends in the traffic fatality data, from 1899 to the
present, is presented in a separate write up.
IoKsMTxStudy Page 5 of 60
Introduction
This is the second of a two-part article prepared by the author, prompted
mainly by a recent news item about attempts by the Texas legislature to
increase the speed limit to 85 mph, at least in some parts of the state. The
speed limit in Texas now is 80 mph, with Utah being the only other state
with this high a speed limit. 85 mph would be the highest posted speed limit
in the United States and the second highest in the world. A speed of 140
kmph (86 mph) is posted in some parts of Poland.
http://en.wikipedia.org/wiki/Speed_limits_in_the_United_States
http://www.reuters.com/article/2011/04/07/us-texas-speed-limit-idUSTRE7366L720110407
http://www.huffingtonpost.com/social/Dana1982/texas-speed-limit-may-rea_n_847269_84007982.html
The problem that we are trying to address here is a very simple one. We
simply do not seem to agree on what all the data that is being compiled
meticulously, by various government and law enforcement agencies, about
highway fatalities really means, especially the effect of increased speed
limits in various states on the highway fatalities.
Proponents of increasing the speed limits point to low fatality numbers from
Montana, for example, just 27 for the 12 month period in 1998-1999, when
Montana law only specified reasonable and prudent as the recommended
speed. This was the law from December 1995 to June 1999 and fatalities
jumped to 56 in the following 12-months when a 75 mph speed limit was
imposed. Some other states, where speed limits were increased, also
revealed a reduction in fatalities after the increase. Proponents of reduced
speed limits, on the other hand, point to data from states where fatalities
increased after the speed limits were raised.
The argument has also been made that the number of fatalities per se is
not a good measure and that fatality rates, not fatalities, must be
considered. Fatality rates could be adjusted to reflect population, or
registered motor vehicles, or licensed drivers, or vehicles miles traveled
IoKsMTxStudy Page 6 of 60
(VMT), the last being the most commonly used, see NHTSA http://www-
fars.nhtsa.dot.gov/Main/index.aspx . The fatality rate per 100 million VMT is
thus taken to be the relevant statistic. However, as noted in the earlier
report by the author, the fatality rates, based on the VMT, for the US taken
as a whole, have been declining year after year, since 1921. This fatality
rate has dropped to a historical low of in 2010.
Touting a low VMT based fatality rate is tantamount to the argument that it
is somehow better to die in a fatal crash after driving a thousand miles from
one‟s home than after driving a thousand yards. One of the most important
arguments against the VMT-based fatality rate is the justified criticism of
VMT inflation. VMT values can easily be inflated to arrive at a low fatality
rate, since, unlike fatality, VMT is an estimated, not a measured, quantity.
Texas Proofing of Vehicles
Ideally, we would like to reduce, if not completely eliminate, fatalities on our
highways. We know that the higher the speed at which one travels the
higher the (kinetic) energy that must be absorbed when a crash does
occur. The laws of physics teach us that the kinetic energy K of an object
(the energy possessed by an object by virtue of its motion) increases as the
square of the speed, K = ½ mv2 where m is the mass of the object and v its
speed. (The symbol v is used in physics to denote velocity, which is speed
in a given direction.)
This means that the energy that must be absorbed in a crash occurring
when a vehicle is traveling at 65 mph has increased by 40%, at 70 mph it
has increased by 62%, and so on, see Figure 1. At 80 mph, the current
speed limit in Texas and Utah, it has increased by 112% and at 85 mph,
the limit that the Texas legislature is pushing, it has increased by 139%.
In other words, vehicle design and engineering must adjust to these new
realities of the increased desire by drivers in Texas or Utah or Montana to
drive at much higher speeds than elsewhere in the nation. Very soon, car
manufacturers must “Texas-proof” the cars they sell. Just imagine the ad
campaign, with the label Texas Proof stamped to a pickup or SUV, like we
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have liquors that have higher and higher “proof” numbers depending on
their alcohol content!
Figure 1: Graph indicating the increase in the relative amounts of energy that
must be absorbed in a crash with increasing speed of the vehicle. If the kinetic
energy of a vehicle traveling at 55 mph is set at 100, its kinetic energy is 140 at 65
mph (40% increase) and 162 at 70 mph (62% increase) and so on. At 80 mph, the
current speed limit in Texas, the energy that must be absorbed has more than
doubled (112% increase). At 85 mph, which is the limit being pushed by Texas
legislature, the energy that must be absorbed has increased by 139% compared to
the energy that must be absorbed when the same vehicle is traveling at 55 mph.
IoKsMTxStudy Page 8 of 60
We also know, from overwhelming statistical data, that speeding is one of
the most prevalent factors contributing to traffic crashes and the resulting
fatalities. There are three types of crashes: fatal, injury (i.e., non fatal) and
property damage only. Crash data compiled annually by the National
Highway Traffic Safety Administration (NHTSA), suggest that speeding was
a factor in 30% of all fatal crashes, as highlighted in the following reports.
http://www-nrd.nhtsa.dot.gov/Pubs/810998.pdf
Traffic Safety Facts: 2007 Data DOT HS 810 998
http://www-nrd.nhtsa.dot.gov/Pubs/809915.pdf
Traffic Safety Facts: 2004 Data DOT HS 809 915
http://www-nrd.nhtsa.dot.gov/Pubs/811402EE.pdf
Traffic Safety Facts 2009
Furthermore, as we see from the above, speeding is usually also a factor in
alcohol-related fatal crashes. It is also a factor in more than 34% of fatal
crashes that occur on wet roads (rain), in 55% of fatal crashes under snowy
conditions and over 57% of fatal crashes under icy conditions. Also, it
should be noted that speeding-related fatal crashes occur on both
interstates and non-interstate roads, under all types of posted speed limits,
from ≤ 35 mph to ≥ 55 mph.
Given these facts, it would seem that the recent attempts to increase the
speed limits on our highways are misguided. It should be noted, however,
that a number of very reasonable arguments are made by proponents of
the no speed limit laws. This is an unending debate, which pits individual
freedom against perceived societal good. Attention is called to some of the
pros and cons cited by both sides, briefly, in appendix 1.
http://www.hwysafety.com/MDT_reply_82001_section3.htm
http://safety.transportation.org/htmlguides/speeding/section01.htm
According to NHTSA, traffic fatalities in 2010 have dropped to their lowest
levels in recorded history. http://www.nhtsa.gov/PR/NHTSA-05-11
IoKsMTxStudy Page 9 of 60
Between 2009 and 2010, the number of traffic fatalities fell nearly 3%, from
33,808 to 32,788. Fatalities have dropped 25 percent since 2005, from a
total of 43,510 fatalities in that year. Statistical projections indicate that the
fatality rate will be the lowest on record since 1949, with 1.09 fatalities per
100 million vehicle miles traveled, down from 1.13 for 2009. This decrease
in fatalities for 2010 occurred despite an estimated increase of nearly 21
billion miles in nationwide vehicle miles traveled.
It would be tragic if this momentous trend is reversed with the recent
attempts to increase the speed limits on our highways. The significance of
these historical trends in fatality data were discussed in detail in the first
part of this article, see link below,
http://www.scribd.com/vlaxmanan
Does Speed Kill? Forgotten Facts of US Highway Deaths in 1950s and
1960s.
Between 1965 and 1966, public pressure grew in the US to increase the
safety of cars. The deaths on US highways had been increasing year after
year. In 1966 Congress held a series of highly publicized hearings on
highway safety. This led to the legislation for mandatory installation of seat
belts, which also created the US Department of Transportation (on Oct 15,
1966). As President Lyndon B. Johnson stated at the signing of the
National Traffic and Motor Vehicle Safety Act on September 9, 1966,
" ... we have tolerated a raging epidemic of highway death ... which has killed
more of our youth than all other diseases combined. Through the Highway Safety
Act, we are going to find out more about highway disease—and we aim to cure it."
Accordingly, the main purpose here is to take a fresh look at the traffic
fatality data, especially the data from Iowa, Montana that has been
prominently by both proponents and opponents in this speed limit debate.
http://www.iowadot.gov/mvd/ods/stats/2006speedstudy.pdf
A significant increase in fatalities was observed in Iowa, after the speed
limit was raised on rural interstates to 65 mph in May 1987 and also when it
IoKsMTxStudy Page 10 of 60
was raised once again, to 70 mph, in July 2005, see link given above.
Indeed, according to this study, all the Midwestern US states that increased
the speed limits (to 65 mph) showed an increase in fatalities ranging from 7
to 13 percent (see extract from above report in appendix 1). In Montana, on
the other hand, the number of fatalities dropped dramatically immediately
after the reasonable and prudent (i.e., no numerical limit) law was adopted.
Does the traffic fatality data, recorded immediately before and after the
changes, warrant the conclusions drawn? Is there indeed a correlation
between posted speed limits, and/or raising or lowering them, and the
traffic fatalities? This is the question that we would like to answer, using a
reliable scientific approach. In what follows here, a new methodology is
described, which is based on the analysis of both the number of traffic
fatalities (F) and the number fatal crashes (C) recorded over the years. The
merits of this approach will become obvious when we reconsider the Iowa
and Montana traffic fatality data for the past several decades.
The benefits of decreasing the speed limit (to just 35 mph) in Utah, during
the war years, were unequivocal. The only county, where fatalities
increased, seems to have been the county with chronic speeders.
1940 - 1949 / War Speed Limit
http://publicsafety.utah.gov/highwaypatrol/history_1949/war_speed_limit.html
On October 28, 1942, a War Speed Limit of 35 mph came into effect in an attempt to conserve
gasoline and save on tires. Enforcement began on November 10, 1942. Many cars were operating
with unsafe tires because people were unable to buy new tires.
With the implementation of the War Speed Limit of 35 mph, Patrolman Russ Cederlund was
featured on the cover of the November 1942 issue of Public Safety, a national magazine devoted
to promoting public safety. Patrolman Cederlund and Matt Haslam of the state road shop are
shown replacing a 50 mph sign with a 35 mph sign. Because all of Utah’s 40, 50 and 60 mph
signs were reflectorized, all of these signs had to be replaced. The old signs were stored in
anticipation that the speed limit would be raised following the war.
Despite a 5 percent increase in motor vehicles in Utah from 1941 to 1943, Utah had a significant
decrease in accidents, injuries, and fatalities. The following chart represents this decrease:
IoKsMTxStudy Page 11 of 60
Although vehicle miles traveled decreased 11 percent, fatal accidents in Utah decreased by 50
percent, the ninth lowest in the United States. Utah was the only state in the nation with an
increase in motor vehicle registrations during this period of time. The only area of the state
which showed an increase in fatal accidents was Utah County. Colonel Pete Dow immediately
transferred two patrolmen from the southern district to assist the Utah County personnel in
slowing down the many "chronic speeders" in Utah County.
Data available for scientific analysis
The following three pieces of pertinent data are readily available from
various sources on the Internet and can be used in a scientific analysis of
the effect of increasing speed limits on the number of fatalities in our
roadways. This also highlights areas where improvements are needed in
our data collection and/or organization.
Number of Fatalities, F
Number of fatal crashes, C
Fatality rates (based on VMT)
IoKsMTxStudy Page 12 of 60
However, if one wishes to seriously study the effect of increasing the
(legal) speed limits, which is usually restricted to interstate highways, it is
important to look at these three numbers ONLY as they apply to rural
and urban interstates. Fatality and crash data on other types of roadways
are less relevant. For example, the following F and C data is readily
available for Texas at the TxDOT website. However, corresponding values
of the VMT, for rural and urban driving, is not available. This is the single
most important shortcoming in data reporting (both state and nationwide).
Table 1A: Texas Interstate Traffic Fatalities-Crashes Data (2003-2009)
Year 2003 2004 2005 2006 2007 2008 2009 Rural, C 218 188 221 206 149 174 130 Rural, F 259 238 292 242 178 212 150 Urban, C 279 284 285 272 306 270 236 Urban, F 327 321 319 286 338 300 250
Only fatal crashes and fatalities occurring on interstate highways are included here.
Source: Texas Department of Transportation (TxDOT), Motor Vehicle Crash Statistics
ftp://ftp.dot.state.tx.us/pub/txdot-info/trf/crash_statistics/2009_update/12_2009.pdf
ftp://ftp.dot.state.tx.us/pub/txdot-info/trf/crash_statistics/2003_update/12_2003.pdf
In many cases, only fatalities (F) are reported without recording the
corresponding number of crashes (C), see data for Alabama, given below.
Fatalities in urban areas are generally lower than in rural areas, see
Alabama data, because crowded driving promotes greater alertness and
caution. Rural driving, with reduced traffic, on the other hand, promotes
inattentiveness, tendency to dose off and/or veer off the road and also risk
taking at super high speeds. The Texas data, however, defy this logic.
Table 1B: Fatalities in Alabama Interstates (1998-2007)
Year 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Total 1023 1028 1118 1110 1033 1040 1082 1113 1142 1190 Rural 634 665 754 742 661 722 727 749 757 772 Urban 389 363 364 368 372 318 355 364 385 418
Source: 1997 ALABAMA TRAFFIC ACCIDENT FACTS. Note that information
on the corresponding fatal crashes or the fatality rates (interstate VMT) is missing.
http://documents.crdl.ua.edu/docs/1997FactBook.pdf
IoKsMTxStudy Page 13 of 60
Also, methods must be developed to improve VMT estimates, specifically
as it applies to interstate highways, to avoid the criticism of VMT inflation/or
deflation, to arrive at a desired fatality rate. With these caveats, we will now
take a fresh look at the fatality data in three states: Iowa, Montana, and
Texas, because of some unique aspects of the data and all because this
data has also been analyzed before by other authors.
Before we proceed, let us quickly review the Utah war-years data since this
reveals an important property of traffic fatality statistics.
Figure 2: Graph of accidents versus fatalities in Utah during the war years when
the war speed limit of 35 mph was adopted in the state. The number of fatalities
appears to increase at a fixed rate as the number of accidents increase. Here
―accidents‖ includes all types – not just those that led to a fatality. The slope of the
straight line through the three points can be estimated using classical linear
IoKsMTxStudy Page 14 of 60
regression analysis. However, here we use the average value of the three slopes
obtained by consider any two of the three points in the data set. This average slope
h = 0.0475. (The slope of the best-fit line h = 0.478.) Since the straight line must
pass through all three points, the intercept c can be fixed by considering any one
data point. The equation of the straight line is y = hx + c and considering the (x, y)
values for 1942 we get c = - 86.23. This line can be seen to pass very close to the
(x, y) pairs for 1941 and 1943.
Notice that the both the VMT, x, and the number of fatalities, y, decreased
during the war years. The fatality rate, determined by the ratio y/x, also
decreased each year, from 13.58 in 1941 to 9.83 in 1942 and to 7.6 in
1943. The fatalities/accidents ratio also decreased from 0.034 to 0.03 to
0.026. The average value of this latter ratio is 0.0301. The x-y graph, of
accidents versus fatalities, reveals a nice linear trend, see Figure 2, with
the three data points falling almost on a perfect straight line. The equation
of this line is of the type y = hx + c = 0.0475x – 86.23, where the numerical
values of the slope h and intercept c were determined as described in more
detail in the figure caption. The fixed slope h = 0.0475 means that fatalities
increase at a constant rate as the number of accidents increase: we expect
475 additional fatalities per 10,000 additional accidents, or about 5
additional fatalities per 100 additional accidents. (The graph of VMT versus
fatalities, on the other hand, does NOT reveal such a nice linearity.)
The near-perfect linear trend observed in the war-years is almost certainly
due to the low speed limit. Vehicles of this era were obviously built very
differently from modern vehicles and had few safety features (not even
good tires, as noted in the article cited). Even a collision at a low speed led
to fatalities. However, even today, fatalities are observed at all speeds in
our roadways; see, for example, the annual Traffic Safety Facts 2009 by
NHTSA, link below, Tables 59 and 60 and Figure 24, even at ≤ 30 mph.
http://www-nrd.nhtsa.dot.gov/Pubs/811402EE.pdf
The greater predictability in the war-years data is certainly due to less
variability in road and driving conditions. It also suggests that the universal
IoKsMTxStudy Page 15 of 60
law describing the relation between the number of accidents and the
number of fatalities is a simple linear law, y = hx + c where x is the number
of accidents (or fatal crashes) and y is the number of fatalities. As we will
see shortly this universal law appears to be confirmed when we consider
the more recent data for the states of Iowa, Kansas, Montana, and Texas.
From the nature of the trends observed, there is little doubt that the same
would also be confirmed if we consider the data for every state and also the
national data, or even international data from other countries. This linear
law was already alluded to in the earlier report (see conclusions and also
discussion of Figure 4 in that first report).
Finally, when we consider all types of
accidents, or crashes (which includes those
resulting in injuries only and property
damage only), the constant h, as we see
here for Utah, has a very low value (less
than 1, or even 0.10, ≈ 0.05). Its value
cannot be predicted theoretically.
However, if we consider only fatal
crashes, and the law y = hx + c still applies,
the slope h = 1, ideally, since a single
crash must produce one fatality, 2 crashes
2 fatalities, and so on. Also, ideally, the
constant c = 0, since the number of
fatalities y must go to zero as the number of
crashes x goes to zero.
In the real world, h > 1, see sidebar, and
the greater the deviation from 1, the higher
the rate at which fatalities increase due to a
variety of factors (speed limits, road
conditions including weather, type of roadway, vehicle infrastructure, driver
behavior, and so on). Also, the constant c will be non-zero and can be
either positive or negative.
Fatal crashes at County Level
If we consider data at the
county level, for example, in
2009, in Michigan, there were
2 fatal crashes and exactly 2
fatalities in Manistee county,
i.e., (C, F) = (2, 2). In Alcona it
was (3, 3), Isabella (9, 9),
Jackson (12, 12). In other
counties, there were more
fatalities per fatal crash.
Example Macomb (37, 41),
Oakland (51, 53), Wayne
(149, 173). For the state as a
whole it was (806, 871).
http://www.michigantrafficcr
ashfacts.org/doc/2009/quick_
2.pdf . For the US a whole, it
was (30,797, 33,808) in 2009.
IoKsMTxStudy Page 16 of 60
Iowa Motor Vehicle Fatalities data
From 1970 to 1974 the speed limit on Iowa rural Interstates was 75 mph. In
1974, following the Arab oil embargo of 1973, a National Maximum Speed
Limit (NMSL) of 55 mph was imposed and adopted throughout the US
(reluctantly by some states). The Iowa speed limit was 55 mph.
Table 2: Fatal Crashes and Fatalities in Iowa
Year Crashes, x (fatal)
Fatalities, y F/C ratio, y/x
Comments on speed
limits
1970 38 57 1.50 75 mph day 1971 25 31 1.24 and 65 mph 1972 35 37 1.06 speed limit 1973 41 48 1.17 at night. 1974 23 24 1.04 NMSL takes 1975 29 40 1.38 effect in 1974 1976 20 27 1.35 I speed limit 55 1977 19 21 1.11 mph until 1978 27 28 1.04 1986. 1979 19 20 1.05 1980 22 30 1.36 1981 28 35 1.25 1982 15 22 1.47 1983 17 21 1.24 1984 13 15 1.15 1985 13 18 1.38 1986 13 14 1.08
1987 21 23 1.10 Up 65 mph on May 12, 1987
Average (1970-1986)
1.23
Last 4-yr. avg. 35 43 At 75/65 mph First 4-yr avg. 23 28 At 55 mph Last 4-yr avg. 14 17 At 55 mph
Source: http://www.iowadot.gov/mvd/ods/stats/2006speedstudy.pdf
IoKsMTxStudy Page 17 of 60
In 1987 the NMSL was partially repealed and speed limits were allowed to
increase to 65 mph. In 1995, the NMSL was fully repealed and each state
could set its own speed limit. In 2005, Iowa increased its rural interstate
speed limit to 70 mph.
Table 3: Fatal Crashes and Fatalities in Iowa
Year Crashes, x (fatal)
Fatalities, y F/C ratio, y/x
Comments on speed
limits
1988 28 35 1.25 Speed limit 1989 26 28 1.08 was 65 mph 1990 23 27 1.17 from 1988 1991 25 32 1.28 to 2004 1992 25 29 1.16 on all rural 1993 29 34 1.17 Interstates 1994 26 36 1.38 I in Iowa 1995 19 26 1.37 1996 20 30 1.50 1997 29 32 1.10 1998 25 34 1.36 1999 32 38 1.19
2000 35 41 1.17 2001 30 39 1.30 2002 22 25 1.14 2003 24 38 1.58 2004 16 23 1.44
2005 38 47 1.24 70 mph on July 1, 2005
Average (1988-2004) 25.53 32.2
1.27
First 4-yr avg. 26 31 At 65 mph Last 4-yr avg. 23 31 At 65 mph
The fatality-crashes data for the period 1970-1987 and for 1988-2005 are
reproduced in Tables 2 and 3 were obtained from a report released by Iowa
Department of Transportation, see links given below.
IoKsMTxStudy Page 18 of 60
http://www.iowadot.gov/mvd/ods/stats/2006speedstudy.pdf
http://www.topslab.wisc.edu/workgroups/TSC/Speed_Limit_Lit_Review-
Updated_071405.pdf Impact of Raising Speed Limits onTraffic Safety, by
Arup Datta and David A. Noyce
Let us first consider the data for the more recent period, 1988-2005, in
Table 3. The authors of the above report compared the fatalities after the
speed limit was increased on July 1, 2005 with the average fatalities in the
first and last four year periods (1988-1991) and (2001-2004), see last two
rows, before the increase. An average of 26 crashes, with an average of 31
fatalities, were observed during the first-four year period at 65 mph. Fewer
crashes, 23, with exactly the same average number of fatalities were
observed in the last-four year period of the 65 mph era. The number of fatal
crashes and fatalities jumped to 38 and 47, respectively, when the speed
limit was raised to 70 mph.
Can we now say, unequivocally, based on these four-year-average-fatality
calculations, that the jump in 2005 was entirely due to the higher speed
limit? Or, are there other factors, besides the increased speed limit, that
must be considered to assess this situation?
Or, consider the situation before the adoption of the NMSL of 55 mph. In
the last-four year period (1970-1973) before the NMSL, the average
crashes and fatalities were 35 and 43, respectively. In the first four-year
period after adoption of 55 mph, the number of crashes had dropped to 23
and the fatalities had dropped to just 28. Was this again entirely the result
of the lower 55 mph speed limit? Likewise, in the last-four year period
(1983-1986) of the 55 mph speed limit, the average number of crashes and
fatalities had dropped even more to 14 and 17, respectively. Was this again
the beneficial effect of the 55 mph speed limit over a long and sustained
period? It then increased again in 1987, after the partial repeal of NMSL.
A careful examination of all of the data in Tables 2 and 3, at both the 65
and 55 mph speed limits, suggests the following.
IoKsMTxStudy Page 19 of 60
1. The number of fatalities, y, is always greater than the number of
crashes, x. By definition, a fatal crash is a crash where there is at least
one death. Often, however, more than one person dies when there is a
fatal accident. The fatalities/crashes ratio F/C ratio, or y/x, is always
greater than 1.0. This is indicated in the calculations in the fourth
column. The average value of the F/C ratio, or y/x ratio, is 1.27 in the
more recent period (1988-2005) and 1.23 in the earlier era (1970-1987).
2. The higher the number of crashes the higher the number of fatalities.
Considering the period 1988-2005, Table 3, with 20 crashes, there were
30 fatalities. With 30 crashes, there were 39 fatalities. With 25 crashes,
there were only 34 fatalities. With 35 crashes, there were 41 fatalities.
And so on. This suggests that the x-y scatter graph must have a nice
upward trend. The data here suggests that with x = 10, y = 9, and the
rate of change h = y/x = 9/10 = 0.9. Many such values of the slope h
can be calculated and an average determined. The classical statistical
method, known as linear regression analysis (also called least squares
method), permits a determination of the slope of the so-called best-fit
line through many such (x, y) pairs.
The graphical representation of the fatalities-crashes data from Table 3
indeed reveals a nice upward trend, see Figure 3. The best-fit line through
the data points has the equation y = hx + c = 1.215x + 0.118 where the
slope h = 1.215 and the intercept c = 0.118. Ideally, the intercept c = 0
since we know that y = 0 when x = 0, i.e., when the number of crashes
goes to zero, the number of fatalities must also be zero. The small positive
value of the intercept is the result of statistical variations (see also the brief
discussion in appendix 1 on this point). Many factors besides being in a
crash determine if the occupant will actually die – age and prior health also
being significant factors that cannot be overlooked. Also, the rapid access
to emergency medical services (EMS) determines whether a severely
injured occupant can survive. Furthermore, the age and condition of the
vehicle and how well it is maintained (apart from the basic manufacturer‟s
vehicle design and engineering) could be contributing factors that make a
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bad situation worse in the event of a crash. All such factors introduce
statistical “noise” and affect the numerical value of the constant c in the
linear law y = hx + c revealed here.
Notice also that the slope of the best-fit line h = 1.215 is comparable to the
average slope h = 1.23 determined from the seventeen values of the y/x
ratio in Table 2. Indeed, it can be shown that as the number of data points
increases, the average slope h would ultimately tend asymptotically to the
value determined using the linear regression analysis.
Figure 3: Graphical representation of the fatalities-crashes data for the period
(1970-1987). A nice upward trend is revealed here which simply means that the
higher the number of (fatal) crashes, the higher the number of fatalities. The
classical statistical method known as linear regression analysis yields the best-fit
equation y = 1.215x + 0.118. The correlation coefficient r2 = 0.831 implies a
IoKsMTxStudy Page 21 of 60
strong positive correlation between the variables x and y considered here. One can
now extrapolate using this equation to predict the number of fatalities with higher
or lower number of crashes, x. This also permits an unbiased assessment of the
effect of increased speed limits on our highways. The best-fit equation can be used
to predict the number of fatalities for 35 crashes, the average number of crashes in
the last-four year period (1970-1973) before the adoption of the NSML of 55 mph.
It can also be used to predict the number of fatalities immediately following the
repeal of the NSML and the new higher speed limit. Amazingly, for x = 35, the
best-fit prediction yb = 42.64 or 43 fatalities, exactly what was calculated in the
earlier report. Also, for x = 21, yb = 25.63 or 26 fatalities. The actual number of
fatalities observed after the partial repeal of the NSML in May 1987 was just 21.
Since the number of fatalities will increase or decrease, as the number of
crashes increase or decrease, we can estimate the number of fatalities by
simply extrapolating from the best-fit line. Predictions of the number of
fatalities based using the best-equation suggest that the higher fatalities
observed in the four-year period, before the adoption of the NSML of 55
mph, and in the year immediately after its partial repeal in 1987, are
consistent with the predictions of the best-fit equation for the period when
the speed limit was 55 mph.
The number of fatalities increased in 1987, and again in 2005, because
the number of fatal crashes also increased. The increase in fatalities
is consistent with the predictions based on an extrapolation from the
best-fit equation deduced for the 55 mph era. Thus, it is clear that the
higher speed limits in 1970-73, or in 1987, did not play any statistically
significant role.
This is confirmed by the graphical representation of the pre-NSML data
(with speeds limits of 75/65 day/night) and 1987 data following the partial
repeal of NSML in 1987 (65 mph). The five solid dots in Figure 4 represent
this data and are simply superimposed on to the earlier plot of Figure 3.
With just one exception, (38, 57) for the year 1970, the other four data
points lie on or very close to the best-fit line deduced from the analysis of
the data for the 55 mph speed limit. This implies that the universal law y =
IoKsMTxStudy Page 22 of 60
hx + c holds at all speed limits and the number of fatalities y increase or
decrease as the number of crashes x increase or decrease. The higher
fatalities observed after the speed limit was increased are not significantly
higher than the fatalities that would have been observed, at the lower
speed limit. Hence, the speed limit per se does not affect the number of
fatalities and is not a significant contributing factor.
Figure 4: Graphical representation of the fatalities-crashes data for the period
1970-1987. The five solid dots represent the data for the four years prior to NSML
(1970-1973) and the single year following the partial repeal of NSML (1987). Four
out of five data points fall at or close to the best-fit line deduced by considering
only the data for the NSML era. This means that the speed limits per se do not
affect the number of fatalities observed here, or account for the increased number
of fatalities. We are merely observing the universal law y = hx + c with fatalities
increasing as the number of (fatal) crashes increase. Factors other than the speed
IoKsMTxStudy Page 23 of 60
limit are probably the reason for the higher number of fatalities observed in 1970
and can be investigated to arrive an improved understanding of this problem.
The reason why the 1970 data point (38, 57), at the higher speed limits
(75/65) appears as an outlier on this graph certainly needs further
investigation. The higher fatalities in this instance are most likely due to
factors unrelated to the speed limit per se, some of which have been
mentioned briefly already. Notice also that for the year 2005, when higher
speed limits (70 mph) were again introduced, 38 crashes produced 47
fatalities, see Table 3, and also the data graphed in Figure 5.
Figure 5: Graph of the Iowa fatalities-crashes data for 1988-2005. The average
value of the F/C ratio for these years is 1.273. A linear regression analysis can
once again be carried out to determine the best-fit line through the data points.
This is presented in Figure 5. Instead, here we first consider first the dashed line
IoKsMTxStudy Page 24 of 60
with the equation y = 1.273x with the slope being the average value just
determined. This passes through the origin (0,0) and the data can be seen to follow
this line quite closely, with some scatter. Quite amazingly, the data point (38, 47)
for 2005, at the higher speed limit, falls almost exactly on this line, suggesting that
the higher fatalities observed in 2005 were due entirely to the higher number of
crashes and not the increase in the speed limit.
Consider now the best-fit line through the points in Table 3, see Figure 6.
Once again, we see that the data for 2005, when the speed limit was 70
mph, follows the extrapolated best-fit line, and falls just above it. Some
additional comments are relegated to appendix 2.
Figure 6: Graph of the Iowa fatalities-crashes data for 1988-2005, with the best-fit
line y = 0.908x + 8.99, through the data points. The best-fit line has a finite
positive intercept c = 8.99 which means that when crashes x = 0, there is still a
IoKsMTxStudy Page 25 of 60
finite number of fatalities y = 9 (whole number). Also, the slope of the best-line h =
0.908 is less than 1 whereas all observations indicate that the F/C ratio > 1. (This
is also true if we consider data from other states and for the US a whole. The F/C
ratio is always greater than 1.) However, the statistical basis of linear regression
analysis is a very sound one and this suggests that factors other than just the
increased speed limit must be carefully considered to understand the difference
between the two sets of data. In both cases, the increase in the number of crashes
and led to the increase in the number of fatalities but the circumstances
surrounding these crashes, and hence the number of fatalities must also be
considered more carefully. Nonetheless, the effect of increased number of crashes,
as opposed to the speed limit per se, is evident even if we use the best-fit line to
extrapolate to determine the number of fatalities.
Finally, for completeness, the composite graph which includes all the data
from Table 2 and 3, for 1970-2005, is presented in Figures 7 and 8. The
different data symbols represent data for different speed limits. The dashed
line, in Figure 8, with the equation y = 1.25x has a slope h = 1.25, which is
the “average” value of the slope for the two data sets in Tables 2 and 3.
The best-fit line through the data points was also recalculated. The slope h
= 1.200 is higher, see Figure 8, representing the influence of the data from
all the speed limits. More importantly, the intercept c is now very nearly
zero, having just a small positive value of c = 1.02. All the data points, from
all the different speed limits are scattered around this recalculated best-fit
line suggesting no significant effect of the speed limit per se. The number
of fatalities increased because the number of (fatal) crashes increased.
Hence, rather than being distracted by the divisive debate regarding the
speed limit, we should focus on understanding the reasons why a crash,
especially a fatal crash occurs and develop control strategies to either
minimize or eliminate such crashes.
IoKsMTxStudy Page 26 of 60
Figure 7: Composite plot of all the Iowa fatality data for 1970-2005, confirming
the linear law y = hx + c. Different symbols are used to denote data generated
during the years with different speed limits. A significant positive deviation of an
individual data point from the best-fit line, or the line with the ―average‖ slope h
= 1.23, implies that special factors that led to increased fatalities in that year need
more careful investigation. Fewer crashes actually led to more fatalities in that
year, even with the same speed limits prevailing.
This does NOT imply that higher speed limits are of NO consequence and
must be whole heartedly embraced. It only means that we must understand
the underlying reasons why a fatal crash occur, with the high speed limit
being just one of many contributing factors.
IoKsMTxStudy Page 27 of 60
Figure 8: Composite plot of the Iowa fatality data for the years 1970-2005. The
solid line with the slope h = 1.20 is the recalculated best-fit line. This has a very
small positive intercept c = 1.02. The dashed line has the ―average‖ slope h =
1.23 considering both data sets from Tables 2 and 3.
One important factor that continues to be important, in spite of the
strict seat belt laws enacted in practically all states, is the very high
correlation between fatality and the failure to use seat belts.
Perhaps, manufacturers should be required to ensure that seat belts
are automatically deployed and the vehicle made inoperative when
seat belts are not used – not only by the driver but also by every
single passenger – just as we have sensors that tell us when any
single door is not properly secured/closed.
IoKsMTxStudy Page 28 of 60
The Montana No Speed Limit Safety Paradox
http://en.wikipedia.org/wiki/Speed_limits_in_the_United_States#No_speed_limit
http://www.us-highways.com/montana/mtspeed.htm
A typical speed limit sign at the Montana state line from December 1995 to June
1999. On March 10, 1996 a Montana patrolman issued a speeding ticket to a
driver traveling at 85 mph (136 kmph), on a stretch of State Highway 200.
Although the officer gave no opinion as what would have been a reasonable speed
limit, the driver was convicted. He appealed to the Montana Supreme Court. The
court reversed the conviction on December 23, 1998. It held that the law requiring
drivers to drive at a non-numerical ―reasonable and proper‖ speed limit is so
vague that it violates the Due Process Clause … of the Montana Constitution.
Effective May 28, 1999, the Montana Legislature therefore established a speed
limit of 75 mph (121 kmph). Technically speaking, Montana had no speed limit
until June 1999.
http://www.hwysafety.com/hwy_montana_2001.htm
http://www.motorists.org/press/montana-no-speed-limit-safety-paradox
http://www.hwysafety.com/MDT_reply_82001_section3.htm
IoKsMTxStudy Page 29 of 60
http://forums.thecarlounge.com/showthread.php?2553995-Are-Speed-
Limits-Really-Necessary
The data and findings given below, including the highlighted tables, are
extracted verbatim from the article by Chad Dornsife (link above).
Interstates: 4 Lane Divided
1998: No Daytime Speed Limits
Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec
4 0 2 4 5 1 5 4 0 1 3 2
Jan - June Average Month: 2.7 July - Dec Average Month: 2.5
1999: No Daytime Speed Limits
75 Maximum Speed Limit
Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec
2 2 4 2 1 0 2 7 4 1 1 4
Jan - May Average Month: 2.2 June - Dec Average Month: 2.7
2000: 75 Maximum Speed Limit
Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec
4 2 8 5 2 7 7 3 4 1 6 7
Jan - May Average Month: 4.7 June - Dec Average Month: 4.7
Last 12 months/No Daytime Limits
2000: W/Speed Limits Reinstated
27 Fatals / Modern Low 56 Fatals / Modern High
Here is what the Montana data shows (chart below). After all the politically correct
safety programs were in place and fully operational, complete with federal safety
funds, more laws and citations being issued, here are the results.
IoKsMTxStudy Page 30 of 60
1. After the new Speed Limits were established, interstates fatal accidents went
up 111%. From a modern low of 27 (11 + 16 for June 1998 –May 1999)
with no daytime limits, to a new high of 56 (28+28 in 2000) fatal accidents
with speed limits.
2. On interstates and federal primary highways combined, Montana went from
a modern low of 101 with no daytime limits, to a new high of 143 fatal
accidents with speed limits.
3. After a 6 year downward trend in the percentage of multiple vehicle
accidents on its 2 lane primary highways, multiple vehicle accident rates
increased again.
4. With the expectation of higher speed when there was no daytime limit,
Montana’s seat belt usage was well above the national average on its
highways without a primary law, lane and road courtesy increased, speeds
remained relatively stable and fatal accidents dropped to a modern low.
After the new limits, fatal accidents climbed to a modern high on these
classifications of highway, road courtesy decreased and flow conflict
accidents rose again.
All the important observations made in original research paper remain very
germane in regards to this doubling of fatal accidents on Montana’s highways.
(February 2000, Montana: No Speed Limit Safety Paradox) The following excerpts
tell the story.
“Research scientists and engineers have long known that there are sometimes
unexpected results from changes in public policies. Ironically, the paradox of no
posted speed limits and low fatal accidents rates is no surprise to the traffic
safety engineering community.” End of verbatim quote from Dornsife.
1996, Officer Steve Wisniewski.
http://www.montanatrooper.com/userfiles/fall2010/fall_2010_cover_story.pdf
IoKsMTxStudy Page 31 of 60
Counterpoint: The tabulated data from Dornsife supports point 1 above.
The same data also permit a different interpretation. Consider the non-
consecutive periods of Jan-June 1998 and June-Dec 1999. Between Jan-
June 1998, when there was no daytime speed limit in Montana, the total
fatalities was 16 and the 6-month average was 2.7 (16/6 ≈ 2.7 ), the same
as the average for the 7-month period (19/7 ≈ 2.7) from June-Dec 1999,
when the 75 mph speed limit was imposed. In other words, there is NO
SIGNIFICANT CHANGE in the monthly average fatalities.
State data from NHTSA: The following data was obtained from the
NHTSA annual reports entitled Traffic Safety Facts. For 1998, Table 106 of
page 160 indicates that there were 30 fatal crashes in rural interstates in
Montana and 0 fatal crashes in urban interstates. The total fatal crashes
and fatalities (Table 104) were 208 and 237, respectively, including all
types of roadways.
Montana Rural and Urban Interstates Fatalities-Crash data
Year Rural
crashes
Urban
crashes
Rural
fatalities
Urban
fatalities
1997 50 1 58 1
1998 30 0 33 0
1999 35 1 41 1
2000 30 4 33 4
2001 35 2 40 2
2002 48 0 59 0
2003 43 0 47 0
2004 37 1 40 1
Source: NHTSA Annual Reports, Chapter 5. Notice the huge contrast with Texas.
For 1997, Table 106 of page 154 states that there were 50 fatal crashes in
rural interstates in Montana and 1 fatal crash in urban interstates. The total
fatal crashes and fatalities (Table 104) were 223 and 265, respectively,
including all types of roadways. The information on fatalities in the rural
and urban interstates was similarly obtained from accompanying tables.
IoKsMTxStudy Page 32 of 60
Notice the big difference in the number of rural interstate fatal
crashes, 50 and 30, for 1997 and 1998, both years for which Montana
had the Reasonable and Prudent speed law. The corresponding
fatalities were 58 and 33. In other words, such large year-to-year
variability, or even month-to-month variability, in the data is expected
and does not necessarily have anything to do with the speed limit.
The jump for 27 to 56 fatalities, between 1999 and 2000, as noted by
Dornsife, is nothing out of the ordinary.
http://www.ibiblio.org/rdu/a-montge.html http://www.ibiblio.org/rdu/dotst-mo.html
Figure 9: Fatalities-Crashes data for Montana (1997-2004) obtained from the
annual NHTSA Traffic Safety Reports (chapter 5). For 1997 and 1998, Montana
had the Reasonable and Prudent (R & P) speed law. The data points (51, 59) and
IoKsMTxStudy Page 33 of 60
(30, 33) for these two years is indicated by the two filled diamonds. The equation
of the straight line joining these two points is y = hx + c = 1.24x – 4.14. All the
other data (solid dots) are with the 75 mph speed limit. The fatalities data after the
introduction of a numerical speed limit follows this straight line (deduced with the
R & P speed law). Fatalities increase as the number of crashes increase. Notice
also the very large change in the number of fatal crashes in the two years with the
R & P speed law.
Figure 10: Montana statewide fatalities-crashes data for the most recent period
1994-2009. The NSML was fully repealed in 1995. Notice that the same universal
relation is revealed. Furthermore the numerical value of the constant h in the
relation y = hx + c also appears to be roughly constant when we consider
IoKsMTxStudy Page 34 of 60
fatalities-crashes data for rural and urban interstates (Figure 9) or all roadways
taken together.
Finally, as seen in Figures 10 and 11, the universal fatalities-crashes law is
also confirmed when we consider the Montana fatalities data for all
roadways for the recent period 1994-2009 (after the repeal of NSML in
1995 and the R&P law in 1999) and also the earlier period 1978-2009, with
NSML. The data for all these periods follows a nice linear trend, suggesting
again that speed limits per se do not affect the number of fatalities. The
number of fatalities only seems to depend on the number of crashes.
Figure 11: The statewide Montana fatality-crash data for the period 1978-2009,
with different speed limits. All data, regardless of the prevailing speed limit follow
the same straight line y = hx = 1.142x where the slope h of the straight line is
taken as the average value of the F/C ratio for all the years taken together.
IoKsMTxStudy Page 35 of 60
Figure 12: The Montana data for the period 1978-2009 with the best-fit line
superimposed on to the data along with the straight line with a slope equal to the
the “average” value of the fatalities/crashes = F/C ratio. This is called the
“average” slope line. This average slope h = 1.142 is very nearly equal to the ratio
m = ym /xm = 241/211 = 1.142 where xm and ym are the average values of x and y.
Both these lines, the one with the “average” slope and the best-fit line always
passes through the point (xm,ym). The line with average slope (ym/xm) passes
through the origin whereas the best-fit line pivots about the point (xm,ym) and
makes a finite positive or negative intercept on the y-axis. This pivoting of the
best-fit line occurs because, mathematically, the best-fit is an attempt to minimize
the squares of the vertical deviations (y – yb) of each data point from the best-fit
trend line; see also the discussion in appendix 1.
IoKsMTxStudy Page 36 of 60
Additional comments on the Montana data
Montana DOT data: The following information was obtained from the
report by Montana DOT, see link below, which provides the fatalities and
crash data for the 10-yr period 1997-2006. According to the data in Table 1,
the total number of fatalities was exactly the same, 237, in 1997, with R & P
speed law, and also in 2000, when the speed limit was 75 mph.
http://www.co.missoula.mt.us/healthpromo/DUITaskForce/pdfs/2008StateR
eport.pdf
Montana’s scenery. Photo of Butte, MT provided by driving enthusiast John
Watne, Montanabahn vs Autobahn http://home.comcast.net/~jwatne/autobahn.htm
The higher fatality number for 2000 given here is because fatalities in all
roadways is included, not just the fatalities on the Interstates. There were
208 fatal crashes in 1997 and 203 fatal crashes in 2000 but the 5 fewer
crashes in 2000 still produced the same total fatalities.
IoKsMTxStudy Page 37 of 60
Also, from Table 3 of this report, we see that the fatality rate (per 100 M
VMT) was actually higher in 1997 (2.84) and 1998 (2.50), with no numerical
speed limit, compared to 2000 (2.40) suggesting a beneficial effect of the
speed limit.
http://lubbockonline.com/news/021597/in.htm
The above, from 1997 Lubbock Avalanche-Journal, includes brief
comments following the debate in the Montana legislature on the speed
limit. One lawmaker argued that a limit is need because traffic deaths on
Montana's interstates doubled from 1995 to 1996: from 16 to 32. Added
Attorney General Joe Mazurek: ''I'm glad the Senate debated it, but I can't
help but ask: How many people have to die before we need a speed limit?''
http://www.deseretnews.com/article/466857/MONTANA-TROOPER-SAYS-
DRIVERS-ARE-MISTAKEN-ABOUT-SPEED-LIMIT.html
http://books.google.com/books?id=u_kSIrzxxKQC&pg=PA316&dq=montan
a+1997+interstate+fatalities&hl=en&ei=HLjpTYCdIuru0gGAn5WgAQ&sa=X
&oi=book_result&ct=result&resnum=2&ved=0CD4Q6AEwAQ#v=onepage&
q=montana%201997%20interstate%20fatalities&f=false
Montana: The Great Experiment by Kevin Atkinson. The second link above
gives the % of drivers exceeding various speeds when there was no
numerical speed limit is Montana. In Urban Interstates, only 5% exceeded
75 mph and none exceeded 80 mph. In rural interstates, 8% exceeded 75
mph and less than 3% exceeded 80 mph and under 1% exceeded 85 mph.
http://leg.mt.gov/content/Publications/Audit/Report/98l-11.pdf
http://nakedlaw.avvo.com/2011/05/would-highways-be-safer-with-no-
speed-limits/
http://www.ipenz.org.nz/ipenztg/papers/2002/11_Patterson.pdf
http://www.us-highways.com/montana/mtspeed.htm
IoKsMTxStudy Page 38 of 60
The Texas Interstate Traffic Fatalities-Crashes
Letter: Don't reward lawbreakers with higher speed limits Posted April 15, 2011 at 5:51 p.m
http://www.reporternews.com/news/2011/apr/15/dont-reward-lawbreakers-with-higher-speed-limits/
Why on earth are we raising our speed limits in Texas?
It is a proven fact that lower speed limits at around 55 mph make most cars get better gas
mileage. We should be lowering them, not raising them………………
******************************************************************************
As we see from Table 1A and Table 1B, urban fatalities in Texas are
significantly higher than rural fatalities. Is this due to the much publicized
higher speed limits in Texas?
However, if we look at the pattern so far, this may be simply be due to the
higher number of urban crashes in Texas. The linear law, y = hx + c,
relating crashes and fatalities applies for both sets of data, see Figure 13.
Also, and interestingly also, extrapolating to higher number of crashes
using the rural best-fit line, it is clear that the number of urban fatalities in
Texas is indeed significantly lower. Alternatively, extrapolating from the
urban best-fit line shows that the number of rural fatalities is significantly
higher. This suggests a more careful study of the nature of crashes in these
sections of the Texas interstates and also the emergency responses
available to crash victims.
IoKsMTxStudy Page 39 of 60
Figure 13: Graph of fatal crashes versus fatalities in rural and urban Interstates
in Texas. The data reveals a very high positive correlation between crashes, x, and
fatalities, y, with a high +ve value of the correlation coefficient r2.
Texas Motor Vehicle Crash Statistics – 2009 http://www.txdot.gov/txdot_library/drivers_vehicles/publications/crash_statistics/default.htm
2009 l 2008 l 2007 l 2006 l 2005 l 2004 l 2003
Furthermore, and even more significantly, we see that the best-fit line has a
negative intercept c for both rural and urban data. Theoretically speaking,
when the number of crashes goes to zero (x = 0), the number of fatalities
must also go to zero (y = 0). Hence, the ideal value of the constant c = 0
IoKsMTxStudy Page 40 of 60
and the best-fit line must pass through the origin. However, as we see
here, in the real world the intercept c is sometimes positive (as in the data
for Iowa, this means higher fatalities than should be theoretically achieved,
for the number of crashes) and sometimes negative, as we see here for
Texas.
This actually means that the number of fatalities in both rural and
urban interstates is less than what might be observed if c = 0. The
data for Montana reveals the nearly ideal situation (c ≈ 0), with the
intercept c having a very small positive value. However, the Texas
data shows that even further reductions in fatalities are responsible.
Additional discussion of the significance of the constant c in the linear law,
y = hx + c, relating crashes and fatalities, is relegated to appendix 1.
Selection of Iowa statewide crash-fatality data
at various speed limits
Year Speed limit,
mph Fatal Crashes, x Fatalities, y
1970 75 752 912 1973 75 682 813 1975 55 578 674 1976 55 663 785 1986 55 388 441 1989 65 452 515 1993 65 399 457 1995 65 446 527 1997 65 411 468 2005 70 399 451 2006 70 386 439 2009 70 337 370
Average 491 571 Source:http://www.iowadot.gov/crashanalysis/pdfs/historicaltravelcrashesfatalitiesrates_1970-2009_20100706.pdf
IoKsMTxStudy Page 41 of 60
Iowa Statewide Crash Data and Changing Speed Limits
Finally, to illustrate the effect of both the speed limit and the efficacy of the
(fatal) crash-fatalities analysis emphasized here, consider the following
statewide data for Iowa. The historical data from 1970-2009 has been
compiled by the Iowa Department of Transportation and made be found at
the link given below.
http://www.iowadot.gov/crashanalysis/pdfs/historicaltravelcrashesfatalitiesrates_1
970-2009_20100706.pdf
Figure 14: Graph of the statewide Iowa fatal crashes-fatality data which covers the
40-year period 1970-2009 when Iowa had four different speed limits: 75 mph (data
indicated by filled triangles) in 1970-1973, dropping to 55 mph (filled diamonds)
IoKsMTxStudy Page 42 of 60
on Jan 1, 1974. The speed limit was raised to 65 mph (filled squares) on rural
interstates on May 12, 1987. In 1996, the speed limit was raised to 65 mph in rural
4 lane highways and on July 1, 2005 the speed limit was raised to 70 mph (filled
circles) on rural interstates. The open circle near the center of the graph is the mean
point (xm, ym). The best-fit line passes through this mean point. The data reveals a
near-perfect positive correlation with a regression coefficient r2 = 0.999. Perfect
correlation would be indicted by r2 = +1.000. The crash-fatality data at different
speed limits simply follow this best-fit line.
Although only a small selection of the data, extracted in the table here, has
been considered, the statewide observations reveal a remarkable trend
with near-perfect correlation between the number of fatal crashes and
fatalities, even with changing speed limits. The higher the number of fatal
crashes, x, the higher is the number of fatalities, y. It appears that exactly
the same number of crashes and fatalities might have been observed if
there had been no change in the speed limit.
However, it must be pointed out that the 40-year data considered here
does indicate that the two of the highest crash numbers were observed at
the highest speed limit of 75 mph (the two triangles near the top of the
graph). Also, the three lowest crash numbers occurred at 70 mph (the filled
circles near the bottom of the graph), after the most recent change in the
speed limit in July 2005. The 55 mph and 65 mph data fall in the middle.
Hence, it appears that instead of entering into a futile debate on the speed
limits, greater attention must be paid by traffic researchers and safety
experts to understand the conditions and factors that
Lead to a crash in the first place.
Promote survival of the vehicle occupants in the event of a crash
and/or minimize their injuries. (Sometimes, unfortunately, third
parties, such as pedestrians, bicyclists, etc. are killed in a motor
vehicle crash, especially in other third world countries, where a
motorist has to combat a variety of other transportation methods.)
In addition to the speed limit, and the urgent need to “Texas Proof” vehicles
of the future by various manufacturers as speed limits continue to rise,
IoKsMTxStudy Page 43 of 60
ultimately it is the interaction of the following that determines the type of
vehicle that will be offered to the consumer in the future.
First, there can be no doubt that a lower speed offers more control and
ability to avoid a crash in an emergency situation, or when road hazards
are encountered unexpectedly (could even something as simple as a sharp
bend on the road, which led to a fatal crash recently with a photograph of
the crashed vehicle, as highlighted in the earlier report).
Second, a manufacturer must consider the interaction of the following:
Speed → Crash → Safety → Weight → Fuel economy
All these factors must be taken together to arrive at a societal compromise
which dictates vehicle design and engineering and what is offered to the
consumer. The higher the vehicle weight, the lower the fuel economy,
although such a heavier vehicle would probably be more crashworthy and
promote safety of its occupants in a crash. Safety and crashworthiness are
tied to speed which determines the energy that must be absorbed by the
vehicle infrastructure.
There is also the legal ramification of how much any vehicle manufacturer
should be expected to do in terms of vehicle design and engineering to
keep a driver in Texas safe, in a crash at 90 mph or 100 mph. Just like
CAFÉ standards and emission standards led to the development of all
electric (GM‟s EV) and hybrids, rising speed limits will force manufacturers
to either rebel and force back such laws, or innovate! There was never a
better time to be a materials scientist in charge of developed advanced,
high strength and lightweight materials that could be manufactured at a
cost lower than dirt.
Lighter than air (not quite!) – Stronger than steel - Cheaper than dirt!
Does the need to meet CAFÉ standards conflict, from a purely technical
standpoint, with the need to keep vehicle occupants safe in Texas?
Indeed, the discussion of exactly these factors was the topic of a workshop
IoKsMTxStudy Page 44 of 60
sponsored recently (on Feb 25, 2011) by NHTSA (details included as
appendix 2 with links to presentations by various experts).
http://www.nhtsa.gov/Laws+&+Regulations/CAFE+-
+Fuel+Economy/NHTSA+Workshop+on+Vehicle+Mass-Size-Safety
Even in Montana, when the law only specified a “reasonable and prudent”
speed, motorists, especially out-of-state motorists, found themselves being
ticketed for speeding and failing to obey the reasonable and prudent
standard. One such driver challenged his ticket (although convicted) and
went to Montana Supreme Court which then agreed that the Montana law
was so vague as to be unconstitutional. Lawmakers were therefore forced
to adopt the numerical 75 mph speed limit. 80 mph or 90 mph or even 100
mph might seem safe, or reasonable, or even prudent to a few (perhaps,
the 15% who always seem to be traveling above the posted speed limit, if
one accept the 85th percentile rule to fix the speed limit). However, they still
have to share the road with the remaining 85% whose lives cannot be
threatened and who must not be put in a dangerous situation to avoid a
collision with the happy speedster!
Texas Legislator Pete Gallego unveiling a new 80 mph speed limit sign on
Interstate 10 near Fort Stockton, Texas.
IoKsMTxStudy Page 45 of 60
Kansas Speeding-related Crashes-Fatalities
Year 1990 1991 1992 1993 1994 1995 1996 1997
Crashes, x 123 103 93 93 91 105 112 99 Fatalities, y 142 118 106 105 101 116 122 109 Speed limit 65 65 65 65 65 65 70 70
Year 1998 1999 2000 2000 2001 2002 2003 2004 2005
Crashes, x 113 108 108 106 111 119 112 94 100 Fatalities, y 123 129 119 113 134 140 127 114 118 Speed limit 70 70 70 70 70 70 70 70 70
Year 2006 2007 2008 2009 2010 2011 2012 2013 2014
Crashes, x 111 89 87 n/a n/a Fatalities, y 118 99 97 n/a n/a Speed limit 70 70 70 70 70 75 75 75 75
http://www.marc.org/Transportation/safety/pdf/2000%20Kansas_Traffic_Accident
_Facts_Book.pdf Data for 1990-2000
http://www.ksdot.org/burTransPlan/prodinfo/accista.asp Click on speed to get data
for 1998-2008
******************************************************************
The Kansas legislature recently approved an increase in the speed limit to
75 mph, as reported in the Wichita Eagle on April 4, 2011 (see link below).
http://www.kansas.com/2011/04/10/1801633/will-higher-speed-limit-mean-
more.html
An officer of the Kansas Highway Patrol thinks this means drivers will be
doing 80 or 85 mph. Does it necessarily mean more accidents or more
deaths? The data compiled here, however, yields conflicting interpretations.
Considering only the speeding-related crashes in Kansas, there were
exactly 111 crashes in 2001 and again in 2006 but with 134 fatalities in
IoKsMTxStudy Page 46 of 60
2001 as opposed to only 118 in 2006. The speed limit was the same in
both years. On the other hand, 103 crashes in 1991, when the speed limit
was 65 mph resulted in 118 fatalities. The same fatalities were reached
with just 100 crashes in 2005 when the speed limit was raised to 70 mph.
The crashes-fatalities graphs, presented in Figures 15 and 16 again reveal
no significant effect of the speed limit. The data for both speed limits clearly
overlap and follow the best-fit equation relating crashes x and fatalities y
deduced by considering the data for the 70 mph era.
Figure 15: The data for speeding related crashes are readily obtained from the
Kansas Department of Transportation website (see links given). As seen here,
when the number of crashes x increases, the number of fatalities y increases and
seems to follow the predictions based on classical linear regression analysis. The
IoKsMTxStudy Page 47 of 60
linear regression coefficient r2 = 0.698 is quite high. As included is straight line
the ―average‖ slope which passes through the mean point (xm, ym). The best-fit line
also passes through this point but pivots to either a higher or lower slope
depending on the ―scatter‖ in the data. The slope of the best-fit line is determined
to minimize the sum of the squares of the vertical deviations of each (x, y) pair in
the data set from the best-fit line.
Figure 16: The speeding-related fatalities-crashes data for 1990-1995, indicated
by the black solid dots, are superimposed here to the graph in Figure 15. These
data are intermingled with the 70 mph data and follow the best-fit line deduced
earlier suggesting no statistically significant effect of the increased speed limit on
the Kansas speeding-related fatalities, after the repeal of the NSML in 1995.
IoKsMTxStudy Page 48 of 60
Finally, the following comments, posted on the internet by readers of the
above news item (on increasing the speed limit in Kansas to 75 mph), are
revealing. It starts with the sad statement from the parent of a young 18
year old who was killed in an accident when he was driving at 65 mph. He
was not speeding. The current speed limit in Kansas is 70 mph.
The Clutter Cutter
My 18 year old son was going 65 mph (NOT
speeding) when he crashed on the turnpike and
yet speed impacted the severity of his crash (he
was killed). When the speed limit is legally raised, I
will NOT be driving that fast. All you have to do is
see what a 65 mph crash does to a car and a loved-
one’s body, and you will never go that fast again.
04/10/2011 02:56 PM
TyrannyResponseTeam
Sorry to hear about your loss but you are unsafe at
any speed in a car. Even sitting at a light.
04/11/2011 03:13 PM
in reply to The Clutter Cutter
ShaneVendrell
Reasonable and prudent...Where can I find some of these huuuuuge tracts of land?
04/10/2011 02:53 PM
Effect of high speeds
Narrowed field of vision (tunnel vision)
Less effective safety cushion of maneuvering space
o Greater stopping distances
Reduced ability to safely negotiate curves,
Reduced ability to react to other motorists encroaching on their lane of travel, and avoid a collision.
Source:
http://www.policechiefmagazine.or
g/magazine/index.cfm?fuseaction=d
isplay_arch&article_id=1001&issue_i
d=92006
IoKsMTxStudy Page 49 of 60
cafanter
Montana was like that in the 90s.
You could set your cruise around
90-100 if you had a newer car. At
night it dropped to 65 and
Montana would warn you at
70mph.
04/10/2011 03:19 PM
milehighks
Yea.. this is good news. Although
this will cutdown on the laughing
at the Colorado drivers who
forget to slow down after they
cross the border.
Tippycanoe
BAD POINTS
1. Cost of signs
2. Fuel Consumption
3. So with the new limit some will
drive between 85 - 90
4. When the turnpike first opened
they would check your speed with
the time stamp on your turnpike
ticket. They found a goodly
number of drivers were running at
triple digits.
National Motorists Association
NMA Position On Speed Limits
Speed limits should be based on sound traffic
engineering principles that consider the actual travel
speeds of responsible motorists.
Typically, this should result in speed limits set at the
85th percentile speed of free-flowing traffic (the
speed below which 85 percent of traffic is
traveling).
These limits should be periodically adjusted to
reflect changes in actual traffic speeds.
http://www.motorists.org/speed-limits/position
Motorists have rights. We've
been protecting them since 1982.
IoKsMTxStudy Page 50 of 60
Summary and Conclusions
1) There is clearly an overwhelming public sentiment in favor of
increasing speed limits, as indicated by the willingness of various
state legislatures (since the full repeal of the National Maximum
Speed Limit of 55 mph in 1995) to increase the speed limits to as
high as 75 mph with Texas being in the forefront, willing to push to
85 mph. Nonetheless, it is also clear, and borne out by indisputable
facts that accidents, or crashes as they are called by traffic safety
researchers, when do they occur at such high speeds (even at 65
mph, when one is not speeding), or even in zones where the posted
speed limit is less than 35 mph, can be tragic and fatal. There is no
escaping the laws of physics and the increasingly higher amounts of
energy that must be absorbed by the vehicle infrastructure to prevent
death and/or serious injuries to the occupant(s).
2) When this study was initiated recently [prompted mainly be the news
about Texas going to 85 mph, and started reviewing fatalities and
fatal crashes data from states like Iowa (with its speed limit
increases) and Montana (with no numerical speed limit) and Texas
(with its highest in the nation speed limit)], the author was fully
expecting an outcome that showed fatalities and crashes going up
significantly after each increase in the speed limit, although he was
aware that fatality rates, based on VMT, have been going down. This
led to the decision to more carefully study the relation between fatal
crashes (C) and fatalities (F) under relatively well controlled
conditions – such as the available data for rural and interstates
crashes or the data for speeding-related crashes.
3) We do not fully understand all the factors that lead to a crash,
especially a fatal crash, and how they are affected by the posted
speed limits. This is actually a futile debate that would never end.
However, we do know that by definition, a fatal crash means at least
one person has been killed. In some fatal crashes more than one
IoKsMTxStudy Page 51 of 60
person is killed. In spite of the many variables and the unknown
variabilities that affect this phenomenon, the data overwhelmingly
shows that fatalities, F, increase as the number of fatal crashes C
increase, in a very statistically predictable manner. A simple linear
law, of the type y = hx + c, seems to describe the relation between
the number of fatal crashes, x, and the number of fatalities, y. Fatal
crashes, rather than total crashes (i.e., we exclude crashes resulting
only in injuries and/or property damage), provides a much better
correlation. Unlike the VMT based fatality rate, which is subject to
the criticism of VMT inflation (VMT is an estimated quantity, not a
measured quantity), both the number of crashes C and the number
of fatalities F can be more reliably measured. (Dr. Leonard Evans, a
leading traffic safety expert and author of a leading book entitled
Traffic Safety, cautions that even something like the number of
fatalities is sometimes difficult to estimate, as in the case of the
sinking of the Titanic, natural disasters, or the deaths due to the 9/11
terrorist attack, and so on. However, traffic fatalities are a bit different
and a more accurate count is certainly possible, although, as noted,
some of these deaths could even be suicides! Thankfully also,
homicides using motor vehicles are rare.)
4) The linear law y = hx + c can be tested under various conditions to
reveal the effects of significant variables such as speeding, alcohol
impaired driving, rural versus urban, interstates versus other
roadways, etc. (provided high quality data is available to sort each
such variable of interest), to determine if there is a significant change
in the numerical values of either the constant h or the constant c.
5) The Iowa data on the number of fatalities and fatal crashes shows
very clearly that there is NO statistically significant effect of the
changing speed limit under which these crashes/fatalities occurred.
The data follows the same straight line with higher crashes simply
leading to higher fatalities. This is also confirmed by nationwide data
(discussed briefly in the earlier report) and the data from other
states, such as Montana, Texas, and Kansas.
IoKsMTxStudy Page 52 of 60
6) The significance of the numerical values of the constants h and c, in
the universal law y = hx + c, must be appreciated. Ideally, the slope
h = 1 and the constant c = 0 since a single crash must produce at
least one fatality, 2 crashes 2 fatalities, and so on, and the number of
fatalities y must go to zero as the number of crashes x goes to zero.
In the real world, h > 1 and the greater the deviation from 1, the
higher the rate at which fatalities increase due to a variety of factors
(speed limits, road conditions including weather, type of roadway,
vehicle infrastructure, driver behavior, and so on). Likewise, if the
intercept c has a high positive value, fatalities are too high for a
given set of conditions. A large negative value of the intercept c, as
we see for Texas, is definitely desired. The significance of these
constants will become more obvious once traffic safety researchers
accept this simple law and study its implications more carefully to
isolate various crash factors and their effect, with higher-quality data.
7) The relation of the constants h and c to the corresponding constants
in Einstein‟s famous photoelectric law is also obvious and must be
explored by traffic safety researchers.
8) The study here points to the urgent need to improve the quality of
data collection, as it pertains to both fatalities F and crashes C, to
reveal the effect of important factors that most researchers accept as
being important. For example, to study the effect of a change in the
speed limit, it is best to look at F and C values for rural and urban
interstates ONLY, not statewide crash and fatality data.
Unfortunately, with few exceptions, such data is not currently
available for all states. Also, historical data, at least at the state level,
going back to the 1950s or 1960s, are not readily available and
should be compiled and researched thoroughly. Nearly 40,000
people die each year in traffic related accidents and more teenagers
die each year in traffic related crashes than many other events that
grab national or international events (as duly noted by Evans).
IoKsMTxStudy Page 53 of 60
9) The complex interaction of vehicle speed, vehicle weight, fuel
economy, safety and crashworthiness, and other economic
ramifications (insurance costs, medical costs) will ultimately decide
what type of vehicles will be on the road and what speed limits are
indeed reasonable and prudent. We must not forget that in the 1950s
and the 1960s, there was a virtual “epidemic” of traffic related deaths
(highlighted in the earlier report by the author) which prompted the
highly publicized Congressional hearings and the subsequent traffic
safety laws that were enacted. Seat belts and airbags, although
originally resisted by manufacturers due to the costs imposed, are
now common place. Mandatory seat belt laws have also been
enacted in practically all states. Yet, even today, the failure to use
seat belts is still one of the most common reasons cited by law
enforcement for a traffic fatality. (Perhaps, legislators who
champion an increase in the speed limits should be persuaded
to write into such laws the mandatory deployment of seat belts,
by vehicle design, before it can be operated!)
10) The 20th century ushered a new era in personal transportation, with
the introduction of affordable automobiles for the masses. Much more
than the need to improve vehicle occupant safety (which certainly
yielded seat belts and airbags), the demand for improvement in fuel
economy, following the energy crisis (triggered by the Arab oil
embargo in 1973, which highlighted US vulnerabilities to foreign oil),
and the need to improve emission standards, ultimately lead to the
development of modern electric and hybrid vehicles. Likewise, a new
era of higher speed limits, can spur innovations in commercialization
of high-strength, light-weight materials. Such advanced materials are
indeed available but are not cost-competitive at this time. The 21st
century can still become a century of innovations, led again by the
automobile and other type of high speed mass transportation. The
automobile and the vast stretches of open highways, with reasonable
and prudent speed laws, or better yet, no posted speed limits at all,
still beckon many a driving enthusiast. Montanabahn or the
Autobahn! We can, and need to, “Texas Proof” our vehicles!
IoKsMTxStudy Page 54 of 60
Heavier Vehicles Are Dangerous and Kill
http://www.slate.com/id/2297796/
Your Big Car Is Killing Me
American cars are getting heavier and heavier. Is that dangerous? By Annie Lowrey Posted Monday, June 27, 2011, at 6:26 PM ET
Like Americans themselves, American cars are getting heavier and heavier every year.
We pay a hidden cost for our fat cars. They may be sucking up less gas, slowing the degradation of the
environment and the warming of the planet. But they have other "negative externalities"….
A working paper released this month by two economists from the University of California, Berkeley,
Maximilian Auffhammer and Michael Anderson, tackles the first question, attempting to put a price tag
on the fatalities associated with big cars. They studied accident data from eight states, identifying the
type and weight of vehicles involved in collisions by their VIN numbers. The researchers confirm that the
heavy cars kill.
Data understate bus deaths
By Alan Levin, USA TODAY June 29, 2011
http://www.usatoday.com/NEWS/usaedition/2011-06-29-bus-
crashesART0_ST_U.htm
NHTSA's failure to track all the accidents has given Congress and the public a false impression that buses
are safer than they are and has thwarted efforts at tougher regulation, safety advocates say. "By
underreporting crashes and fatalities, it has given the industry the political cover they want to go to
(Capitol) Hill and say, 'We are really safe,'" says Jacqueline Gillan, vice president of the non-profit
Advocates for Highway and Auto Safety.
USA TODAY found at least 42 deaths of motor coach occupants and drivers were not reported using
NHTSA's standard definition of a motor coach from 1995 to 2009, the most current year for which data
are available. Since 2003, 32 fatalities were not included.
IoKsMTxStudy Page 55 of 60
Appendix 1
Significance of the intercept c of the best-fit line
Legendre’s Best-fit Line and Einstein’s Work Function
The rather small value of the slope, less than the F/C ratio observed in all
Iowa fatalities-crashes data, is worthy of further discussion. Let us first
recall two important points here regarding the best-fit line.
1. The best-fit line always passes through the point (xm, ym), the
average point of the data set, in our case, the point (26, 32), see
Table 2. The slope of the line through this “average point” is the same
as the “average slope” 1.273 determined here.
2. The best-fit line, also sometimes known as the least squares line,
pivots around the “average point” depending on the “scatter” in the
data. The extent of this pivoting determines the slope of the best-fit
line. How should the slope be determined?
Some data points will lie above the best-fit line and some will lie below it.
The deviation of any single point (y – yb) is either positive or negative,
where yb is the value on the best-fit line. The sum of all deviations ∑(y – yb)
is exactly ZERO. But the square of each deviation, (y – yb)2 will always be
positive and the sum of all the squares ∑ (y – yb)2 will also be positive.
Mathematically speaking, linear regression analysis fixes the slope of the
best line by minimizing the squares of such deviations; hence the term
least squares method. But, as noted by Legendre, in his famous 1805
paper, when he proposed this method (which was immediately adopted,
one of the most rapid acceptances of any statistical method in the entire
history of statistics, see Stigler, link below), the best-fit line, or least
squares line, is just one of many lines that can one legitimately fit
through the “average point”. Each situation, where one observes a “scatter”
merits its own analysis. The best-fit, or least squares, slope happens to be
the easiest to calculate mathematically.
IoKsMTxStudy Page 56 of 60
However, other “real world” or “physical” considerations cannot be
overlooked. Perhaps, the Iowa fatality-crash data (with a slope less than 1,
which is theoretically impossible, since the F/C ratio must be greater than
1, by definition) is a case in point.
This discussion also points us about the fundamental significance of the
numerical value of the constant “c” determined using the best-fit method.
Intuitively, and considering the Iowa data, the constant “c” appears to be
related to the nature and circumstances of the crashes that led to the
fatalities. This must be more fully investigated. To use a phrase from
physics, the constant “c” is like the “work function” introduced by Einstein to
explain the photoelectric effect.
The mathematical equation proposed by Einstein to explain the puzzling
aspects of photoelectricity is also a simple linear equation, of the type y =
hx + c. Very briefly, when light shines on the surface of a metal, electrons
which are normally bound to the atoms of the metal, are ejected. Modern
photocells, widely used in many applications (garage door openers,
security systems, motion sensing applications such as paper towel
dispensers, toilet flushes, etc.) are based on this principle. The electrons
then flow through an electric circuit to make the device work.
The maximum energy of the electron must be less than the energy of the
photon (a particle of light) that is used to eject the electron. The energy of
the photon is hf, where f is the frequency of light and h is the famous
Planck constant. The idea that light can be thought of as being made up of
particles, each with a fixed “bundle of energy” was a revolutionary one back
in 1905 when Einstein proposed this idea. The idea of light being made of
particles, that obey of laws that he had discovered, had been proposed by
none other than Newton himself. However, this particle idea of light had
been rejected by physicists, in favor of the idea of light being a type of
wave motion. Later, Maxwell, proposed the idea of light being a type of
electromagnetic wave - similar to other electromagnetic waves like X-rays,
gamma rays, microwaves, radiation of all types, and all “waves” that are
now widely used to make our cellphones, GPS systems, and other radio
and modern communications work. Here Einstein was actually extending
IoKsMTxStudy Page 57 of 60
and borrowing an important idea introduced by Max Planck to develop
quantum physics, in December 1900.
After discussing some other important aspects of physics, to justify the idea
of a photon, Einstein went on to postulate that the maximum energy E will
be less than the photon energy hf since some “work” must be done by the
photon to eject the electron. This will vary from one metal to another and is
a very complicated matter. To simply the whole problem, Einstein
introduced the concept of a work function W which must be determined
from actual experimental observations. It cannot be predicted theoretically
but the slope h is predicted theoretically, and must be the value that is
consistent with other types of observation on radiation (which Planck had
been studying back in 1900). The photoelectric equation is therefore,
E = hf - W or y = hx + c
Here W is the work function of Einstein. In this equation y = E, the
maximum energy of the electron and x = f, the frequency of light. The
intercept c = - W.
The problem of the relation between fatalities and crashes that we are
considering here is also a very complex one. The analogy between the
constant “c” and Einstein‟s work function W might well be quite appropriate
and bears further study and investigation by traffic fatality researchers.
Complex problems sometimes indeed have simple solutions.
IoKsMTxStudy Page 58 of 60
Appendix 2
NHTSA Workshop on Vehicle Mass-Size-Safety
NHTSA hosted a workshop on the effects of light-duty vehicle mass and
size on vehicle safety on February 25, 2011. Our purpose was to bring
together experts in the field to discuss some of the overarching questions
that NHTSA must grapple with in our upcoming CAFE rulemaking.
Panelists discussed how statistical analysis can help the agency evaluate
the effect of vehicle mass and size on safety, and how consideration of
vehicle structural crashworthiness, occupant safety, and advanced vehicle
design can help inform the agency‟s understanding of what levels of mass
reduction might be appropriate to consider for CAFE rulemaking.
A number of research projects currently are ongoing at NHTSA and other
agencies and in the private sector to help to answer these questions.
NHTSA held the workshop to help kick off the dialogue process between
the agency and stakeholders and to set a good baseline for further
discussions.
The workshop was at NHTSA headquarters. Due to space constraints,
NHTSA offered a streaming live webinar to expand participation. A
recording of the webinar is accessible below, as are printable versions of all
the presentations.
Workshop materials
Webinar recording
Official transcript NHTSA Deputy Administrator Ron Medford Opening Speech
Panel 1: Statistical Evidence of the Roles of Mass and Size on Safety
Kahane, NHTSA, “Relationships Between Fatality Risk, Mass, and Footprint” Wenzel, LBNL, “Analyzing Casualty Risk Using State Data on Police-Reported
Crashes”
IoKsMTxStudy Page 59 of 60
Van Auken, DRI, “Updated Analysis of the Effects of Passenger Vehicle Size and Weight on Safety”
Lund, IIHS, “The Relative Safety of Large and Small Passenger Vehicles” Padmanaban, JP Research Green, University of Michigan Transportation Research Institute
Panel 2: Engineering Realities – Structural Crashworthiness, Occupant Injury and Advanced Vehicle Design
Summers, NHTSA, “Finite Element Modeling in Fleet Safety Studies” Peterson, Lotus, “The Design and Impact Performance of a Low Mass Body in
White Structure” Kamiji, Honda, “Honda‟s Thinking about Size, Weight and Safety” German, ICCT, “Lightweight Materials and Safety” Schmidt, Alliance of Automobile Manufacturers Nusholtz, Chrysler, “Mass Change, Complexity and Fleet Impact Response” Field, MIT, “Innovative Automobile Materials Technologies: „Feasibility‟ as an
Emergent Systems Property” Jim Tamm, NHTSA Fuel Economy Division Chief, Concluding Remarks
How do I comment on the workshop proceedings?
NHTSA strongly encourages interested parties to submit written comment
on the workshop proceedings to the mass-safety docket. We suggest that
you submit your comments by March 30 to ensure that the agency will have
time to consider fully in the upcoming CAFE NPRM.
However, we will leave the docket open throughout the rulemaking period
and encourage you to check back as we will upload new studies and
information as it becomes available. The docket can be accessed at
http://www.regulations.gov; you can input the docket number NHTSA-2010-
0152 at that website and upload comments electronically, or you can
contact Rebecca Yoon (202-366-2992) at NHTSA for assistance with
submitting comments.
IoKsMTxStudy Page 60 of 60
About the author
The author obtained his Master’s (S. M.) and Doctoral (Sc. D.) degrees in
Materials Engineering from the Massachusetts Institute of Technology,
Cambridge, USA. He then spent his entire professional career at leading US
research institutions (MIT, NASA, Case Western Reserve University, and General
Motors R & D Center, in Warren, MI). He holds four patents in advanced
materials processing, has co-authored two books, and has published several
scientific papers in leading peer-reviewed international journals. His expertise
includes developing simple mathematical models to explain the behavior of
complex systems. He can be reached by email at [email protected]
Acknowledgements
The author is grateful for encouraging comments and helpful feedback
provided by friends and colleagues with whom these documents were
shared prior to uploading as public documents.
Disclosure
This document is being uploaded as a public document and available for
using by anyone interested. The author is not currently affiliated with
anyone in the automotive industry and has no personal conflicting interest
in the debate on the benefits of raising or lowering the speed limits. (Just
drive safely and go from Point A to B, has been his philosophy.) This
research was done entirely on the author‟s personal time. He does not
grant the right to use labels such as “Texas Proof”, or anything remotely
resembling it, in any ad campaigns in the future for any commercial
purpose. Permission for such use is, however, freely granted for
noncommercial uses.