Cl..)u~­\t;,~

C-\ TRANSPORTATION

RESEARCH

Number 182, December 1976

CIRCULAR Transportation Research Board, National Academy of Sciences, 2101 Constitution Avenue, Washington, D.C. 20418

"OPERATIONAL EFFECTS OF SECONDARY STOPPING AND RECOVERY AREAS"

As a person drives on any modern highway, he sees "scars" on the unpaved portions of the right-of-way which betray out-of-control vehicles. Black skid marks which lead off the pavement, marred delinea­tors, chipped concrete structures and upturned sod are but a few of these reminders. It does not seem possible that such events can take place on modem highways.

K. A. Stonex (18) explains this phenomenon in the following way: "In spite of all the educational programs, reprimands, dismissal of poor drivers, etc., it is evident that drivers do leave the road simply be­cause they are people and suffer normal human error. " Penn (17) also discovered that faulty driving or human error which is not usually considered in accident research is a leading source of single-car crashes. It is an accepted fact that as long as there is a man­machine combination controlling the path of a vehicle, there is the possibility of a vehicle departure from the roadway. This means that as long as obstacles exist along the roadside, some drivers are going to hit them. An AASHO report W shows that a typical section of existing primary highway has approximately thirty major fixed objects per mile on the roadside.

There are many reasons why a vehicle will Jea\e the roadway and most of them have been the bases for research projects. The California Highway Patrol (16) has performed an extensive study of the causes and characteristics of single car accidents. The roles of alcohol, drugs and natural death in fatal single vehi­cle accidents were studied. "Of seven hundred twenty-two drivers tested, alcohol content was found significant seventy-four percent of the time. The average alcohol content was twenty-two percent by weight or the equivalent of eleven to fourteen drinks containing one ounce of eighty-six proof alcohol for a 175 pound person. Drugs were significantly present in thirteen percent of the cases and natural death about five percent of the time." (16)

Other reports have linked the causes of single

subject areas 22 highway design 24 roadside development 51 highway safety 53 traffic control and operations

vehicle accidents to speed, falling asleep, roadside hazards, mechanical failure and driver inattentive­ness. This last term, driver inattentiveness, is one term which is associated with most accidents. Whether his senses are dulled by alcohol, drugs, or the lack of sleep or his attention is drawn from his driving task by distractions inside or outside the vehicle, the driver becomes involved in a single vehicle accident when he "overdrives" his attention level.

There are cases of mechanical failures, but a majority of these can be traced back to a form of driver inattentiveness - improper care for his vehicle. The person who fails to have his vehicle lubricated and checked periodically, drives on bald or very cheap tires, or drives excessively hard is causing many of these mechanical failures.

Another study (0 conducted at the University of North Dakota attributed a large majority of fatal single-vehicle accidents to suicidal motivations. An engineer is almost helpless when it comes to eliminating suicidal attempts or to increasing driver attentiveness. The only solution might be to eliminate all obstacles with which a vehicle could collide.

Various studies have established the value of clear roadsides and the contribution of the many odd bits of roadside furniture to the overall accident rate. There is, of course, an obvious need to remove obstacles close to the traveled way and to provide a moderately forgiving road edge such as paved shoulders and gradually sloping drainage ditches. But should the engineering decisions be based on just single-vehicle accident occurrences or should these decisions be based on data collected on all vehicle departures from the roadway? The latter procedure would result in a better understanding of the problem because it would be based on the entire population of vehicle departures and not a biased sample. Many vehicles leave the roadway without

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being involved in an accident and many others have minor accidents which are never reported because the vehicle could be driven away from the scene. The very high present day automobile insurance rates and the probability that a person's rates will increase for a given period after a reported accident (if his policy is not cancelled altogether) may be reason enough to dissuade a driver from reporting a minor accident. The difference between this driver and the unfortunate driver of a reported accident is the fact that extensive damage or personal injury occurred in the latter's case which necessitated the filing of an accident report. Everyone has read an account of an accident where the vehicle hit the only obstruction along the road for miles. For every one of these incidents, there are many vehicles that leave the road out of control, but somehow manage to safely resume their journeys. As long as a man-machine combination is the main source of our mobility, there are going to be run-off­the-road accidents.

Unfortunately, the recent emphasis on highway safety needs and the concurrent accent on highway beautification directly oppose each other in some cases. One governmental agency is spending the taxpayers' money to remove trees and flatten slopes to clear the roadside for the safe traversing of out­of-control vehicles while another governmental agen­cy is spending the same money not only to remove iJiiiiJuarcb:; dru.l Lo ct11uouflL19e j1.1nky~1ds, but Lilso to plant trees. Trees are being planted today which will have to be removed tomorrow because they will present a hazard to the motorist. It was not too many years ago that highway design e ngineers won ctwctru:; fur Lheir ueauLiiul masterpiece s which in­cluded tree filled medians and natural rock outcrops in the right-of-way. These practices are now con­sidered two of the most hazardous in highway de • ign. The American Association of State Highway Officials h.::is s.::iid th.::it where ae::.thctic::J and safety considera­tions conflict, safety should be the paramount factor affecting the general appearance of the highway. (!l

The engineering profession is faced with a pro­blem of trying to develop a scale for safety. The traditional benefit-cost analysis must be supplement­ed by another conBide1d tion. An eng1neor1ng analysis today requires recognition of three factors: the cost, the effectiveness, and the probability with which one is associated with the other. Current methodologies are not comprehensive enough to deal with the pro­blem of finding the overall cost-effective roadside safety design. Invariably these methodologies assume that a set of alternative designs have already been synthesized and those violating any system constraints have been rejected. For example, decision-tree analysis (13) requires a set of altema -tive designs, the optimality of which cannot be guaranteed. A desired cost-effectiveness method­ology should have the distinct advantage of being able to generate optimal cost-effective designs under various traffic and environmental conditions. The set of cost-effective alternatives thus generated can then be evaluated by the highway engineer with some confidence of arriving at a practical and theoretically sound solution to the problem.

This type of analysis is especially needed when considering vehicle departure from the roadway and clearance of fixed objects from the right-of-way.

First of all, the probability of a vehicle leaving the roadway is very small, except in certain isolated locations. Hutchinson (10) found a maximum of four­teen encroachments per mile per year into the median of a divided highway with an AADT of 31,000. People usually do not drive off the roadway on pur­pose. However, once a vehicle has left the roadway, the probability of it traveling a certain lateral dis­tance from the edge of the pavement decreases as the distance increases. When an engineer is con­sidering the removal of objects from the right-of-way, it would be more meaningful to him if he had proba­bility figures for a vehicle striking the objects, in addition to the benefit and cost values for their re­moval. There must be some distance beyond which it is uneconomical and impractical to remove obstacles.

It is an accepted fact that single vehicle, non­collision accident involvements increase as speeds increase, particularly at speeds of more than sevenfy miles per hour. Until recently, new cars were built with bigger, more powerful engines, quieter rides, and extreme comfort which, when combined together, give the driver a false feeling of speed and safety. Almost every driver at one time or another has ex­perienced the effect of drugs, from simple aspirin to L. S. D . With so many people taking antihistamines, cold pills, penicillin, tranquilizers, etc. , all of

another, it is no wonder that the number of single vehicle accidents is staggering.

Our national mobility by automobile is another reason for the increase in run-off-the-road accidents. Before our pre:rnnt-d.::iy sy• tem of super highways, it was more discouraging to travel long distances. The road demanded the constant attention of the driver; tho largor urban areas were frustrating road blocks which ate up valuable time to traverse; and the average person's "distance gauge" was much lower. Not too long ago a two hundred mile trip was a long trip but now many drivers think nothing of driving five hundred miles per day via the interstate system. Our present day system encourages long-distance, straight through driving, which usually results in

the as -built system, it is up to the engineer and other professionals to make the existing network as safe as possible .

Some engineers are doing something about it. It is estimated that the Clean Up the Roadside Environment (C. U. R. E.) Program in California (6) has saved over 350 lives since 1966. This program has reduced the percentage of hit-fixed-object fatal accidents on freeways in California from 36 percent to 24 percent.

The Texas Transportation Institute has done extensive rese.::irch in the area::; of side slope design, roadside ditches, breakaway-sign supports, guard­rails, and breakaway light standards. As a result of these efforts, the severity of single vehicle accidents has been reduced on Texas freeways.

How far from the edge of the pavement should fixed objects be removed? The distance commonly accepted today in design is thirty feet, although, in many instances, fixed objects located within fifty feet of the pavement have been removed. It is believed that many vehicles leave the roadway and

are not involved in a reported accident. This may be due to the absence of an object to hit, the driving ability of the driver or purely chance. At Cornell Aeronautical Laboratory, as a part of NCHRP 17-1 a number of demonstration projects were conducted to find improved methods for the reduction of traffic accidents. One of the projects concerned itself with the angle of departure and distance traversed by vehicles that left the traveled portion of the highway, John W. Garrett made the following statement in a summary report: (.§_)

There have been relatively few studies of the subject and yet this information could be useful in the clearing of roadside obstacles, the placement of guardrails and in the design of future highway systems.

Garrett also mentioned that caution must be used in interpretation of his facts and figures because only accident involved vehicles were investigated. This has been the shortcoming of every other vehicle departure study except the work by Hutchinson.

SCOPE

The physical area in the highway corridor to be con­sidered by this subcommittee is outside the normal operating paths of vehicular movement. It includes medians and those border areas between the highway shoulders and the right-of-way limits. Encroachment into these areas is for the most part involuntary resulting from vehicles being forced from the normal traveled way as a result of events occurring within the normal traveled way.

Therefore, the study of the geometrics of these marginal areas on vehicular operation includes an analysis of those elements which affect the extent of damage or severity of injury. The physical charac­teristics which would enable the driver to regain control of his vehicle and bring it either to a safe stop or a safe return to the traveled way must also be considered. The geometric elements in these areas would have no effect on the normal traffic flow and usual traffic maneuvers such as passing, weaving, entering or leaving the traffic stream at ramps, turning movements, etc. except where lateral clear­ance might restrict capacity. Nor would these elements have any effect on the speed and volume and other variables usually considered in traffic operations analyses. Two basic conditions are assumed : 1) Where encroachment into these areas is made after a prior collision on the traveled way where the vehicle may have sustained damage and the occu­pants may have been injured. 2) When encroachment was made, for any number of reasons, but the vehicle was not involved in collision prior to leaving the traveled way. In either instance, entrance into the median and border areas may or may not have resulted in additional damage or injury.

STATEMENT OF THE PROBLEM

The basic goal of this report is to determine how to measure and evaluate the effects of the geometric elements on the operation of vehicles encroaching in median and border areas . First it is difficult to

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determine the extent of the problem of out-of-control vehicles encroaching in these areas because of the apparent costs in measuring the frequency or the magnitude of such occurrences. While recorded accident data do illustrate those instances where the drivers were not successful in stopping without in­jury or damage, there has been little information gathered on the number of occurrences where the driver was successful in regaining control sufficient­ly to stop or proceed without damage or injury. Table 1 gives typical accident data that are available to illustrate the extent of the problem of vehicles leaving the traveled way.

Analysis of statistics showed that 22 percent of the total accidents were reported to have occurred beyond the traveled way while 11 percent or one-half of these resulted in striking fixed objects in three major categories shown. Thus, while it is shown that a little more than one accident in five occurred beyond the traveled way, there is no indication of the number of successes where the driver was able to stop or return safely to the roadway without an accident. In addition, there is no indication why some drivers who encorached in these areas were able to avoid a collision and which geometric features may have aided them in accomplishing these maneuvers. All the emphasis has been placed on the geometric characteristics associated with a reported accident.

GEOMETRIC ELEMENTS CONSIDERED

Figures 1 - 3 illustrate typical cross sections of rural Pennsylvania highways, showing in particular the cross slopes in the median, shoulder and border recovery areas. Also shown is the vertical drop off between the edge of the pavement and the outside edge of the graded section which is within the right­of-way. These typical sections illustrate what is considered "generous" clear areas adjacent to the roadway which are now being constructed as a re­sult of the 1966 Highway Safety Act. The majority of existing roadway mileage is substandard when measured against these standard designs. The basic question is how do the geometric elements of not only the older substandard highways but also those now being constructed to current standards affect the out-of-control vehicle encroaching in the median and border areas. Some of the elements that should be considered are

Medians

Types: raised, flush, sod, surfaced; Width: with barriers, without barriers; Cross overs: spacing, design, marking; Barriers: types, locations, offset brackets; and Anti-glare screen: types, color, height, etc,

Border Areas

Contours: abrupt changes in contours; Slopes; Cross-slopes, especially to 30 feet beyond shoulder; Surface type, texture;

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Figure 1.

Figure 2.

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Figure 3.

CLASS 4 (At>T 200,oaoo) •~.ifllll@r~ I& C/S

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CLASS 3 (ADT > soo To 111-\V !\Sl7S)

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Table 1. Accidents involving vehicles leaving the traveled way in Pennsylvania for one year.

Striking Fixed Objects

Guardrail STATE Ilridge 6 Median Trees 6 TOTAL Abutments Darrier Poles

Total Acc. 243,798 932 9,697 12,965

Injury Acc. 80,896 478 3,619 6,334

Fatal Acc. 2,112 36 195 278

Persons Killed 2,425 40 24 3 318

CUT & FII.L SECTIO\IS

(UP To /a')

(ol/U 10')

CLA'SS 5 C.UT

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Drainage ditches, walls, inlets, culverts, pipes; and Each of above elements on various grades.

Obstructions

Guardrail; Bridge walls, curbs; Lighting structures, utility poles, sign posts; Trees, shrubs, rock outcropping; and Fences.

There has been considerable research on most if not all of these design elements. This fact is substanti­ated by the numerous entries in the Term Index and the Bibliography.

FREQUENCY AND NATURE OF VEHICLE ENCROACHMENTS ON ROADSIDE AREAS

John Hutchinson (12) has done a considerable amount of work on measuring and analyzing vehicular depar­tures from the roadway. A concise, brief summary of Hutchinson's experience is contained in a paper he presented at the joint meeting of OECD Research Group S-9 and HRB Committee A2A04 in Washington, D.C., in January 1974. The following section is taken from his paper.

There are a great number of variables affecting the frequency and nature of roadside encroachments and an even greater number of variations in the manner in which these variables appear to have been studied and/or appreciated and controlled, and reflected in research results. Any status-of-knowledge type of discussion of this aspect of the roadside obstacle problem would therefore be enhanced by a list of some of the variables and a collage of some of the research findings and their suggested applications. It would be unfair not to warn the reader that the list of variables is definitely incomplete and the collage of research findings does not, in all cases, represent the very best information presently available.

Usual sources of data on the frequency and nature of roadside encroachments are 1) citizens' complaints, 2) accident records, 3) narrow median barrier repair records and 4) direct observation through surveillance; the opportunity for efficient study and/or control of variables increases in this same order.

There are some encroachment frequency variables that act more or less ubiquitously and others which are more related to high concentrations of encroachments at isolated locations. These are listed separately even though there is much overlap. Many of these same variables also affect the nature of encroachments but, again, a separate list is provided. Any similarity to common listings of "accident variables'' is unavoidable.

Overall Encroachment Frequency (Variables)

Traffic volume and composition; Time of day; Road direction (N, S, E, W); Season (Winter, Spring, Summer, Fall); Regional differences (climate, drivers, etc.); Type of traffic service; Geometric standards (grade, alignment, etc.);

Frequency of ingress-egress points; Maintenance procedures and discipline; Pavement marking and delineation; Skid resistance; and Shoulder width.

Spot Frequency (Va riables)

Clearances; Windbreaks (or venturi sections); Type of ingress-egress design; Median openings (crossovers); Roadside scenery; and Expressive inconsistency (poor signing,

route discontinuity, lane drop, alignment standards change, false delineation, etc.) .

Nature of Encroachments (Variables)

Cross slopes (magnitudes, directions and rates of change);

Width of recovery area; Obstacles (number, spacing, nature); Safety barriers (type, location); Traffic volume; Vehicle type; Shoulders (surface type, width, etc.); and Precipitating circumstances (skidding,

blowout, hydroplaning, etc.).

Overall 'Encroachment Frequency

Hutchinson and Kennedy (11) reported the results from a 3 1/2 year Illinois ~rveillance of vehicle encroachments on the 40 ft median of a 31-mile stretch of fo 11r-lane Interstate Route 74. Encroach­ment frequency increased with traffic volume

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up to a point (about 3000 or 4000 ADT) and then decreased in response to a changing encroachment rate. The encroachr:nent rate for higher traffic volumes, based on an extension of the curve to in­clude data for a brief wintertime surveillance of encroachments on four-lane Kingery Expressway, appears to drop down to a value equal to about 1/ 3 the original rate. A further extension of the encroachment rate curve, based on some California median barrier records and surveillance data from other four-lane and six lane expressways (HRR No. 162, P. 1-29), suggests a more or less constant median encroachment rate of about this same general order of magnitude (54 to 130 per 107 vehic le miles of travel) at traffic volumes at least as high as 95, 000 ADT. In other words, once this "low volume" change in median encroachment frequency occurs, there appears to be a more or less linear increase for higher traffic.

Such a linear increase in median encroachment frequency (constant rate) is not denied by the more recent findings from Interstate highway accident research (1_) which shows an increasing accident rate with volume growth. However, the increase in accident rate is largely due to an increase in the multiple vehicle accident rate which encompasses accidents wherein the vehicles are not necessarily involved in roadside (right or left) excursions. The percentage of single vehicle (ran-off-roadway type) accidents actually decreases with volume, while the

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percentage of multi-car accidents increases. The effects of some other encroachment frequency vari­ables have also been reported (!!). A strong seasonal effect and a direction of travel factor were found, Some of the effects of variables related to high con­centration of encroachments at isolated locations are illustrated in reference 11.

Nature of Encroachments

The Illinois study (!!) presents the distributions of angles of encroachment and distances traveled longitudinally and laterally (from the edge of the pave­ment) during encroachments . The chance of vehicle encounter with an obstacle during encroachment was dependent upon length of travel in the median,

On the basis of these data, it was concluded that a 30 ft width of obstacle-free median with mild cross slopes is the absolute minimum requirement for the relatively safe stopping or control of vehicles encroaching on medians at rural highway operating speeds. A 30 ft clear zone to the right of the pave­ment would also be suggested. If a median barrier is to be considered, a 60 ft width of median allowing 3 0 ft of recovery room on each side would also be suggested. Other research (z) has led to similar conclusions regarding the needed width and cross sectir:m::: fnr rnAdinnfl.

Traffic volume warrants have been suggested for the installc1tion of median barriers. Warrants for roadside guardrail installation have been suggested on the basis of the severity of encroachment conditions presented by magnitude of slope and h-eight of emoarikmenf. (1)

John Glennon (fil developed a schematic illustration of a roadside obstacle and its relation­ship to an encroaching vehicle. This diagram was the basis behind the development of a probabilistic hazard index model to evaluate the effectiveness of roadside safety improvements. Glennon' s model considers:

1. Vehicular roadside encroachment frequencies, a function of the ADT;

2 . The percentile distribution for the lateral displacement of encroaching vehicles;

3, The lateral placement of the roadside obstacle;

4. The size of the object; and 5, The accident severity associated with

thP. obstacle,

Because the accident frequency associated with any one obstacle is so small, the probabilistic modal approach is the best method to irlAntify hazardous roadside situations on a large scale. (1)

In the spring and summP.r of 1968, a six month study was conducted along I-65 from Indiana State Road 131 in Clarksburg, Indiana, to US 31 north of Taylorsville, Indiana, a distance of 70 miles. Three times a week an automobile was driven slowly along this test section in an attempt to locate and measure vehicle departures off the right hand shoulqer. Although the results from this study were never published, the following facts were determined.

Sample Size: 101 departures: 17 accidents

Evidence of stopping 73% No evidence of stopping 27% [In the opinion of field observer (abrupt change in direction, foot steps, end of skidding, tow-truck wheel tracks, etc.)

Vehicles that stopped

Ave. angle of departure 11. 5 deg Ave, lateral displacement 2 9. 7 ft Ave. angle of re-entry 19. 0 deg

Vehicles that did not stop

Ave. angle of departure 7. 2 deg Ave. lateral displacement 14. 0 ft Ave. angle of re-entry 15. 3 deg

Distance traveled parallel to the road

Median 186 ft Average 211 ft

Lateral displacement

Median 23 ft (67% did not travel over 30 ft) Average ~5. 5 .i:l (81'/~ did not travel over

40 ft)

Angle of encroachment

Median 8 :-5 de g Average 10. 4 deg

Di~tdllt.:l:l L1aveled while "out of control" (Parallel to road) [In the opinion of field observer (c1brupt change in direction, foot steps, end of skidding, tow-truck wheel tracks, etc.)]

Median 153 ft Average 176 ft

Number of vehicles traveling beyond R.O.W. fence - 18

Number of "forced" stops - 16 (in the opinion of field observer)

Objects hit causing forced stop (in the opinion of field observer)

Fence 7 Trees 4 Average distance Ditch 1 from shoulder Headwall 1 edge to forced Pipe end 1 stop - 41. 5 ft Guardrail 1 Creek bank _I_

16

The most remarkable result from this study came when the approximate time and location of each departure were checked with the accident records of the Indiana State Police. Only seventeen

of the surveyed one-hundred and one departures were identifiable in the accident records. Either there was a definite weakness in the accident reporting proce­dures or there were many unreported incidents. It is strongly felt that the latter is the case with single vehicle accidents. If the vehicle can be driven away, the driver will leave, not wanting to report an acci­dent to his insurance company.

One geometric feature which did show a posi­tive effect on returning a vehicle safely to the road­way was a slight up-grade outside the ditch line. The impact with the ditch line "awoke" the driver and the up-grade assisted the driver to gain control of his vehicle and make a safe re-entry onto the traveled way.

The Kelly Scientific Corporation (15) did a survey in 1969 of various off-road vehicle detection techniques. The main problem with all the detection techniques is money; either they are too labor intensive and, therefore costly, or too costly to implement on a system wide basis. This survey should be analyzed in detail to determine the general applicability of the various detection techniques. A copy of this publication was not reviewed for this report.

STANDARD OF MEASURE

It is recommended that two standards be used to measure and evaluate a section of highway with respect to operational effects of secondary stopping and recovery areas. The first standard is encroach­ments per mile per year. This measure indicates high encroachment locations and is easy to under­stand.

The ratio, encroachments per accident, should be used as a measure of the "forgivingness" of the secondary stopping and recovery area. When this ratio is high, it is an indication of a forgiving high­way. Conversely, if this ratio is low, it is an indication of poor roadside design.

CONCLUSIONS AND RECOMMENDATIONS

More knowledge is needed on all vehicular departures from the roadway, not just those which result in a reported accident. This kind of research would be time consuming and costly, but is a necessity before a better understanding of the operational effects of secondary stopping and recovery areas can be determined .

Also, better understanding of vehicle behavior once the vehicle has left the roadway is needed. The Texas Transportation Institute (Weaver) has studied the effect of side slope design on the path of an encroaching vehicle, but more research like this is required.

Very little work has been done on secondary stopping and recovery areas on non-freeway facilities where right-of-way constraints usually do not allow a thirty foot clear zone on each side of the traveled way. The subcommittee strongly recommends that research problem statements be prepared to fill this obvious void in past research.

This report does not get into the details en­visioned by Bob Coleman when he started this sub­committee project. It does, however, shed some

light on the nature of vehicle encroachments into secondary stopping and recovery areas.

REFERENCES

1. AASHO. A Policy on Geometric Design of Rural Highways. Second Edition, 1965. 2. AASHO. Highway Design and Operational

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Practices Related to Highway Safety. February, 196 7. 3. Cirillo, J.A., R.L. Beatty, S.K. Dietz, S.F. Kaufman, and J.G. Yates. Interstate System Accidents Resea rch Study - I. U.S. Department of Transportation, FHWA, October, 1970. 4. Dearinger, J.A. and J.W. Hutchinson. Cross Section and Pavement Surface (Chapter 7), Traffic Control and Roadway Elements - Their Relationship to Highway Safety. Highway Users Federation for Safety and Mobility, 1970. 5. Eelkma, R. C. , et al. A Statistica 1 Study on the Relationship Between Mental Illness and Traffic Accidents. University of North Dakota, 1968. 6. Estep, A. C .. The California C. U. R. E. Program. California Division of Highways, paper presented at Group 5-9 Meeting of O.E.C.D., Washington, D.C. January, 1973. 7. Garner, G. R. and R. C. Deen. Elements of Median Design in Relation to Accident Occurrence. Kentucky Department of Highways, November, 1971. 8. Garrett, J. W. Summary Report: Development of Improved Methods for Reduction of Traffic Accidents. NCHRP Report 17-1, paper presented at the AASHO Committee on Traffic, Salt Lake City, Utah, October 17, 1967. 9. Glennon, J.C. A Cost-Effectiveness Priority Approach for Roadside Safety Improvements Programs on Freeways. Texas Transportation Institute, February, 1972. (Also NCHRP Report 148.) 10. Hutchinson, J. W. The Significance and Nature of Vehicle Encroachment on Medians of Divided Highways. Civil Engineering Studies, Highway Engineering Series No. 8, University of Illinois, December, 1962. 11. Hutchinson, J.W. and T.W. Kennedy. Medians of Divided Highways - Frequency and Nature of Vehicle Encroachments. Engineering Experiment Station Bulletin 487, University of Illinois, 1966 (Summarized in HRR 162, 1967). 12. Hutchinson, J. W. Frequency and Nature of Vehicle Encroachments on Roadside Areas. Paper presented at Group S-9 Meeting of O.E.C.D., Washington, D. C., 1973. 13. Haefner, L. E. and E. K. Morlok. Optimal Geometric Design Decisions for Highway Safety. HRB Record 3 71, 1971. 14. Johnson, J.H., C.J. Messer, etal. Roadside Safety Design. Texas Transportation Institute, Texas A&M, College Station, Texas. 15. Kelly Scientific Corporation. Survey of Off-Road Vehicle Detection Techniques. February, 1969. 16. Luethje, D. C. The Role of Alcohol, Drugs and Organic Factors in Fatal Single Vehicle Acci­dents. The California Highway Patrolman, Volume 30, No. 11, January, 1967. 17. Penn, H.S. Causes and Characteristics of Single-car Accidents, Part I. HRB Record 79, 1965. 18. Stonex, K.A. Relation Between the Automobile and the Highway. HRB Proceedings, Vol. 33, 1954.

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BIBLIOGRAPHY

1. AASHO. A Policy on Geometric Design of Rural Highways. Second Edition, 1965. 2. AASHO. Highway Design and Operational Practices Related to Highway Safety. February, 1967. 3. AASHO. Summary of Guardrail Practices of Western Regional States and Recommended Warrants and Design. Washington, D.C., September, 1967. 4. National Safety Council. Accident Facts. 1973 Edition, Chicago, 1973. 5. Agent, K. R. and R. C. Deen. Relationships Between Roadway Geometrics and Accidents. TRB Record 541, 197 5. 6. Baker, J.S. Single-Vehicle Accidents on Route 66. HRB Record 188, pp. 26-43, 1967. 7. Baker, J.S. Discussion of Hugh S. Penn's Presentation. HRB Record 79, 1965. 8. Baker, J. S. Research Summary on Single-Vehicle Accidents. For the ASF, 1968. 9. Baker, Susan P. Injury Control: Accident Prevention and Other Approaches to Reduction of Injury. Insurance Institute for Highway Safety, Washington, D.C. 10. Billion, C. E. and N. C. Parsons. Median Accident Study - Long Island, New York. HRB Bulletin 308, pp. 64-79, 1962. 11. Billion, C.E., A. Taruqin, et al. Effects of Parkway Medians on Driver Behavior - vVestchester County Parkways. HRB Bulletin 308, pp. 36-63, 1962. 12. Beaton, J.L., E.F. Nordlinand R.N. Field. Dynamic Tests of Corrugated Metal Beam Guardrail. HRB Record 174, 1967. 13. Blumenthal, M. and Wuen.lernann, H. A 0tate Accident Investigation. 1968. 14. Cady, C. Highway Hazards: The Blatnik Sub-c.;ummlLLee Has Been Taking a Lo11g, IIard Look at Dangerous Installations Along Highways. National Highway Users Conference, August, 196 7. 15. Cantilli, E.J. and B.Lee. Treatment of Road-side Hazards - Decision and Design. HRB Special Report 107, Washington, D.C., pp. 101 -108. 16. Cassell, A. and Brinton, Jr. How Highway Landscape and Land Form Design Affects Adjacent Property. Better Roads , Tune, i 9 7 0. 17. Cirillo, J.A., R.L. Beatty, S.K. Dietz, S. F. Kaufman and J. G. Yates. Interstate System Accident Research Study - I. U.S. Department of Transportation, FHWA, October, 19 70. 18. Cirillo, J.A., S.K. Dietz and R.L. Beatty. Analysis and Modeling of Relationships Between Accidents and the Geometric and Traffic Character­istics of the Interstate System. U.S. Department of Transportation, FHWA, August, 1968. 19. Coleman, R.R. and W,L. Sacks. An Investiga-tion of the Use of Expanded Metal Mesh as an Anti­Glare Screen. HRB Record 17 9. 20. Cosgriff, R.L., J.J. English and W.B. Rocca. An Automatic System for Longitudinal Control of Individual Vehicles. HRB Record 122. 21. Gribbins, Paul D. Investment Return Analysis: A New Approach for Scheduling Improvements at Hazardous Highway Locations. Traffic Engineering, Volume 28, No. 7, April, 1968. 22. Gribbins, P.D., J.W. Hom, F.V. Beeson and R.D. Taylor. Investigation of Medians and Median Openings on Divided Highways in North Carolina.

North Carolina State University, June, 1966. 23. Gribbins, P.D., J.M. Arey and J.K. Donaldson. Effects of Selected Roadway and Operational Characteristics on Accidents on Multi­Lane Highways. HRB Record 188, pp. 8-25, 1967. 24. Gribbins, P. D. , J. W. Hom, et al. Median Openings on Divided Highways: Their Effect on Accident Rates and Level of Service. HRB Record 188, pp. 140 -157, 1967. 25. Dart, O.K. and L.Mann. Relationship of Rural Highway Geometry to Accident Rates in Louisiana. HRB Record 312, pp. 1 - 16, 1970. 2 6 . De Boer, J.B. Road Surface Luminaire and Glare Limitation in Highway Lighting. HRB Bulletin 298, pp. 56 - 73, 1961. 27. Deakin, O.A. Planting for Screening Head-light Glare and Traffic Guidance. HRB Record 53, pp. 17 -25, 1964. 28. Dearinger, J.A. and J.W. Hutchinson. Cross Section and Pavement Surface (Chapter 7). Traffic Control and Roadway Elements - Their Relationship to Highway Safety. Highway Users Federation for Safety and Mobility, 1970. 29. DeLeys, N.J. and R.R. McHensy. Highway Guardrails - A Review of Current Practice. HRB Special Report 36. 3 0. Economic Consequences of Automobile Accident Injuries, Automobile Insurance ,md Compensation titudy. Voiu1nt::: l, Department of Trunopvrtutiun, Washington, D.C., April, 1970. 31. Edwards, T. C., et al. Break-away Sign Sup-port Collisions by Mathematical Model. HPR-2 (104), CPR - ll - 3550, January, 1968. 32. Edward:3, T.C., T.J. Hirsch and R.M. Olson. Design Criteria for Break-Away Sign Supports. HRB Record 222. 33. Eclkma, R.C., at al. A Statistical Study nn the Relationship Between Mental Illness and Traffic Accidents. University of North Dakota, 1968. 34. Estep, A. C. The California C. U. R. E. Program. California Division of Highways, paper presented at Group S-9 Meeting of O.E.C.D., Washington, D.C., January, 1973. 35. Farren, D.W. Roadside Obstacles - Problems and Solutions. Paper presented at Croup 8 =9 Meeting of O.E.C.D., Washington, D.C., 1973. 3 6. Fatal and Injury Accident Rates. U.S. Depart-ment of Transportation, 1969. 37. Field, R.N. and R.N. Doty. A Dynamic Full Scale Impact Test on a Precast, Reinforced Concrete Median Barrier. California Highway Transportation Agency, 1966. 3 8. Finch, D. M. Roadway Delineation with Curb Marker Lights. HRB Bulletin 336, pp. 105-109, 1962. 39. Finch, D.M. Surface-Mounted Lights on Roadway - Fog Studies. HRB Bulletin 298, pp. 24-34, 1961. 40. Fitzpatrick, J.T. Unified Reflective Sign, Pavement and Delineation Treatments for Night Traffic Guidance. HRB Bulletin 255, pp. 138-145, 1960, 41. Forbes, T. W. Improving Visibility of the High-way and Highway Signs as a Means of Accident Prevention. The Prevention of Highway Injury, Highway Research Institute, Ann Arbor, Michigan, pp. 113-117, 1967. 42. Frick, W .A. Geometric Design Related to Traffic Safety. Illinois Highway Engineer, Volume 20,

No. 2, 1968. 43. Fries, J .R. and L.J. Ross. Headlight Glare vs Median Width. HRB Bulletin 298, pp. 51-55, 1961. 44. Galati, J. V. Median Barrier Photographic Study. HRB Record 170. 45. Garner, G. R. Accidents at Median Crossovers. HRB Record 312, pp. 55-63, 19 70 46. Garner, G. R. and R. C. Deen. Elements of Median Design in Relation to Accident Occurrence. Kentucky Department of Highways, November, 1971. 4 7. Garrett, J. W. Summary Report: Development of Improved Methods for Reduction of Traffic Acci­dents. NCHRP Report 17-1, paper presented at the AASHO Committee on Traffic, Salt Lake City, Utah, October 17, 196 7. 48. Barret, John W. and Tharp, Kenneth J. Development of Improved Methods for Reduction of Traffic Accidents. NCHRP Report 79, 1969. 49. Glennon, J.C. A Cost-effectiveness Priority Approach for Roadside Safety Improvement Programs on Freeways. Texas Transportation Institute, February, 1972. (also NCHRP Report 148.) 5 0. Glennon, J.C. and T. N. Tamburri. Objective Criteria for Guardrail Design. Department of Public Works, Division of Highways, Sacramento, July, 1966. 51. Graham, M. D. New Concepts in Guardrail Design. Civil Engineering, Volume 3 7, No. 1, 1967. 52. Graham, M.D. Research and New Concepts in Highway Barrier Design. New York Dept. of Public Works, Bureau of Physical Research, Albany, December, 1966. 53. Graham, M.D., W. C. Burnett, J .L. Gibson and R.H. Freer. New Highway Barriers - Practical Applications of Theoretical Design. HRB Record 174. 54 . Haddon, William, Jr. The Prevention of Accidents. Preventive Medicine, 1967. 55. Haefner, L. E. and E. K. Morlok. Optimal Geometric Design Decisions for Highway Safety. HRB Record 371, pp. 12-23, 1971. 56. Harris, F.R. and H.R. Cooke. Safety Features of Freeways: Part 2: Designing Freeway Medians, Right Shoulders and Side Slopes. Civil Engineering, Volume 38, No. 9, pp. 61-63, September, 1968. 57. Henault, G.G. andH. Perlson. Research and Development of a Guardrail Section for a High Speed Elevated Expressway. HRB Record 152. 58. Highway Research Board. Geometric Design, Barrier Rails and -Sign Supports - Five Reports. Record 152, 196 7. 59. Hofer, Jr., R. Glare Screen for Divided Highways. HRB Bulletin 336, pp. 95-101, 1962. 60. Huelke, D.F. and P.W. Gikas. Non-Inter­sectional Automotive Fatalities - A Problem in Road­way Design. HRB Record 152. 61. Hutchinson, J,W. Frequency and Nature of Vehicle Encroachments on Roadside Areas. University of Kentucky, paper presented at Group S-9 Meeting ofO.E.C.D., Washington, D.C., 1973. 62. Hutchinson, J.W. The Significance and Nature of Vehicle Encroachment on Medians of Divided High­ways. Civil Engineering Studies, Highway Engineer­ing Series No. 8, University of Illinois, December, 1962. 63. Hutchinson, J. W. and T. W. Kennedy. Medians of Divided Highways - Frequency and Nature of Vehicle Encroachments. Engineering Experiment Sta­tion Bulletin 487, University of Illinois, 1966.

64. Hutchinson, J.W., T.W. Kennedy and H.E. Surman. History of Median Development in Illinois . HRB Record 105. 65. Hutchinson, J .W., W .A. Scott and T .W. Kennedy. Medians of Divided Highways. HRB Bibliography 34, 1963. 66. Hutchinson, J. W. and J. H. Lacis. An Experi­ment with Evergreen Trees in Expressway Medians to Improve Roadway Delineation. HRB Record 105. 6 7. Illumination Engineering Society. American Standard Practice for Roadway Lighting. 1963.

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68. Institute for Road Safety Research SWOV. Roadside Safety Structures . The Nether lands , 19 7 0. 69. Johnson, J.H., C.J. Messer, et al. Roadside Safety Design. Texas Transportation Institute, Texas A &M, College Station, Texas. 7 0. Johnson, R. T. Freeway Fatal Accidents. HRB Record 99, 1965. 71. Johnson, R. T. Median Striping Study. California Division of Highways, 1964. 72. Johnson, R.T. Effectiveness of Median Barriers. HRB Record 105. 73. Johnson, R.T. and H.A. Thomason. Simulation Procedure for Automatic Highway Needs Updating. Jorgenson and Associates, Gaithersburg, Maryland, January, 1968. 74. Jorstad, J. R. Safety Grate for Concrete Flared End Sections. FHWA, May, 196 7. 75. Jurkat, M.R. and J.A. Starrett. Automobile­Barrier Impact Studies Using Scale Model Vehicles. HRB Record 174. 76. Keese, C. J. and C. Pinnell. Effect of Freeway Medians on Traffic Behavior. Texas A &M, Texas Transportation Institute., College Station, 1960. 77. Kelly, K. L. Color and Highway Safety. National Bureau of Standards, Washington, D. C. , 1967. 78. Kelly Scientific Corporation. Survey of Off­Road Vehicle Detection Techniques. February, 1969. 79. Kihlberg, J.K. and K.J. Tharp. Statistical Analysis of Accident Rates and Geometry of the Highway. Cornell Aeronautical Lab., Inc., Buffalo, New York, 1968. 80. Kihlberg, J,K. and K.J. Tharp. Accident Rates are Related to Design Elements of Rural Highways. Cornell Aeronautical Lab., Inc., Buffalo, New York, 1968. 81. Little, Arthur, Inc. The State of the Art of Traffic Safety. Automobile Manufacturers Association, Inc., June, 1966. 82. Laker, I. B. Vehicle Deceleration in Beds of Loose Gravel. Ministry of Transport, Harmondsworth, England Road Research Lab., 1966. 83. Loeffler, N. W. Attachment of Concrete Barrier to Bridge. FHWA, April, 1968. 84. Loutzenheiser, D,W. Design of Safer Road­side Structural Elements. FHWA, June, 1968. 85. Luethje, D. S . The Role of Alcohol, Drugs, and Organic Factors in Fatal Single Vehicle Accidents. The California Highway Patrolman, Volume 30, No. 11, January, 1967. 86. Lundstrom, L.C. Safety Aspects of Vehicle­Road Relationships. General Motors Corporation, June, 1968. 87. Mahoney, T. Application of Motor Vehicle Traffic Accident Statistics to Highway Planning and

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Design in Ontario. Canadian Good Roads Associa­tion, September, 1967. 88. Martinez, J.E. An Analytical Solution of the Impact Behavior of Luminaire Support Assemblies. HRB Record 222. 89. Matson, T.M., W.S. SmithandF.W. Hurd. Traffic Engineering, McGraw-Hill Book Company, Inc.,1955. 90. McHenry, R.R., N.J. DeLeys and J.P.Eicher. Analytical Aid for Evaluating Highway and Roadside Geometrics. HRB Record 371, pp. 36-46, 1971. 91. Michie, J.D. and L.R. Calcote. Location, Selection and Maintenance of Highway Guardrails and Median Barriers. HRB, 1968. 92. Michigan Department of State Highways. Anti-Glare Screen Study. Traffic Research Section, Lansing, March, 1966. 93. Mills, Jr. , J.P. Special Delineators Help Reduce Accidents. Better Roads, pp. 19-20, 1958. 94. Mortimer, R. G. The Effect of Glare in Simulated Driving. HRBRecord 70, pp. 57-62, 1965. 95. Moskowitz, K. and W.E. Schefer. California Median Study. HRB Bulletin 266, pp. 34-62, 1960. 96. Mulinazzi, T .E. A Study of Vehicle Departures from the Roadway. Unpublished report, 1968. 97. Mullin, E.F. Roadside Design to Reduce Injuries. Traffic Engineering. ()n, Nordlin, E.F . .ind R,N, Field. D~rnamic TP.:ots of Steele Box Beam and Concrete Median Barriers. Sacramento Transportation Agency, January, 1968. 99. Nordlin, E.F. and R.N. Field. Dynamic Tests of Box Beam Median Barrier, Series XIV, Interim Report. California Division of Highways, Sacramento. 100. Nordlin, E. F. et al. Dynamic Tests of Con­crete Median Barrier, Series SVI. California Division of Highways, Sacramento, August, 1967. 101. Nordlin, E.F., W.H. Ames and R.N. Field. Dynamic Tests of Five Breakaway Lighting Standard Base Designs. California Division of Highways, Research Report No. M&R 636408. 102. Olson, R. M. Development of Break-away Sign Support Structures. Texas Transportation Institute, December, 1966. 103. Olson, R.M., N.J. Rowan and T.C. Edwards. Break-away Components Produce Safer Roadside Signs. HRB Record 174. 104. Penn, H. S. Causes and Characteristics of Single-Car Accidents: Part I. Record 79, 1965. 105. Reilly, W.R. and D.L. Woods. The Driver and Traffic Control Devices. Traffic Engineering, pp. 49-52, 1967. 106. Rockwell, T. H., V. D. Bhise and D. Shinar. Improving Driver Performance on Curves on Rural Highways Through Perceptual Changes. Ohio State University, Engineering Experiment Station, Transpor­tation Research Center, 1973. 107. Roper, V.J. and G.E. Meese. More Light on the Headlighting Problem. HRB Record 70, pp. 2 9-34, 1965. 108. Rowan, N.J. andT.C. Edwards. Impact Behavior of Luminaire Supports. HRB Record 222. 109. Rowan, N. J. Approach-end Treatment of Channelization - Signing and Delineation. Texas Transportation Institute, Texas A &M, 1963. 110. Rowan, N. J. Marking the Approach-ends of Channelization. Texas Transportation Institute,

Texas A&M, 1963. 111. Rowan, N. J. Optimization of Roadway Lighting Systems. HRB Record 216, pp. 34-4 7, 1968. 112. Sabey, B .E. Road Surface-Treatment and the Change in Skidding Resistance with Speed. England Road Research Lab., 1966. 113. Sacks, W ,A. Effect of Guardrail in a Narrow Median Upon Pennsylvania Drivers. HRB Record 83, pp. 114-131, 1965. 114. Shoemaker, N. E. Research and Design of an Impact Absorbing Barrier for Fixed Highway Objects. Cornell Aeronautical Lab., Inc., January, 1968. ll5. Sielski, M. C. Night Visibility and Traffic Engineering. Traffic Engineering, pp. 28-31, May, 1966. 116. Solomon, D. Accidents on Main Rural High­ways Related to Speed, Driver and Vehicle. U. 8. Department of Commerce, July, 1964. 117. Southwest Research Institute. New Structures Concepts for Highway Safety. For Texas Highway Dept., Deptember, 1969. 118. Spicola, J .A. Break-away Light Poles. Minnesota Highway Department, September, 1967. 119. Stewart, R.G. and V .L. Hill. Non-collision Fatal Accidents: How Many Can Be Prevented? Traffic Safety Research Review, National Safety Council, Volume 3, No. 4, December, 1959. l?.O. Stonex, K.A, Let's Cut Out Single-Car Accidents. The SAE Juurnai, Volume 73, No. 4, April, 1965, 121. Stonex, K .A. The Single Car Accident Pn:,l,lem. SAE paper 811A, Automotive Engineering Congress and Exposition, Detroit, January, 1964. 1Z2. Stonex, K.A. Relatiun::;hlµ Between the Auto­mobile and the Highway. HRB Proceedings, Volume 33, 1954. 123. Stonex, K.A. Ructuslde Design for Safety. General Motors Proving Grounds, Michigan, March, 1960. 124. Stonex, K .A. Requirements of an Obstacle­Clear Roadside . General Motors Engineering Staff, Michigan, January, 1963. 125. Stonex, K.A. Highway Design for Safety. General Motors Proving Grounds, Michigan, October, i96i. 126. Stonex, K.A. Relation of Cross Section Design and Highway Safety. General Motors Corporation, January, 1963. 12 7. Stonex, K. A. Elimination of Highway Traffic Hazards. General Motors Corporation, September, 1964. 128. Starrett, J.A. and I.R. Ehrlich. Highway Center - Barrier Investigation: Part II. Stevens Institute of Technology, Report 113 9, June, 1967. 129. Sweet, R.W. Traffic Safety and the Highway Engineer. HRB NEWS No. 26. 1:rn. Texas Dept. of Highways. Why a Median? 1960. 131. Thompson, J .A. and B. I. Fensler. Economic Study of Various Mounting Heights for Highway Lighting. HRB Record 179, pp. 1-15, 1967. 132. Timms, A.G. State of the Art - Present Guardrail Systems. BPR, Washington, D. C. , December, 1966. 133. Tutt, P.R. Guardrail and the Operation of Highway. Texas Highway Department, November, 1967.

134. Tutt, P.R. and J. F. Nixon. Roadside Design Guidelines. HRB Special Report 107, Washington, D.C., pp. 119-132. 13 5. U.S. Department of Transportation. Handbook of Highway Safety Design and Operational Practices. FHWA, Washington, D.C., 1973. 13 6. Van Wagoner, W. T. Highway Environmental Safety Design Practices: A Topical Review. H.RB Record 332, Washington, D.C., 1970. 13 7. Van Zweden, J. New Highway Barriers Decrease Accident Severity. New York State Department of Public Works, PRR 67-2, June, 1967. 138. Walker, A.E. Road Furniture and Design. Road Research Laboratory, London, England. 13 9. Weaver, G.D. The Relationship of Side Slope Design to Highway Safety. TT!, Research Report 626-2, May, 1970. 140. Weaver, G.D. and A.R. Luedecke, Jr. Designing Safer Roadside Ditches. HRB Record 43 7, Washington, D. C., 1973. 141. Weaver, G. D., E.L. Marquis and A.R. Luedecke, Jr. The Relation of Side Slope Design to Highway Safety. TTI, Research Report 626A-l, March, 1972. 142. Weaver, G.D. and D.L. Woods. Cost­Effectiveness Analysis of Roadside Safety Improve­ments. Presented at the 54th Annual Meeting of TRB, 1975. 143. Westerduin, B. Problems with Roadside Obstacles in the Netherlands. Paper presented at Group S-9 Meeting of O.E.C.D., Washington, D.C., January, 1973. 144. Wilson, W.A. Highway Design and Operation­al Practices Related to Highway Safety in North Carolina. February, 1968. 145. Woods, D.L. Cost-Effectiveness Priority Program for Roadside Safety Improvements on Freeways. TTI, Project No. 2-8-72-11. 146. Wright, P.H., J.S. Hassell and B. Arrillaga. Cross-median Crashes. HRB Record 332, Washing­ton, D.C., 1970, 14 7. Yu, J.C. Driver Performance Related to Median Visibility. Accident Analysis and Prevention, An International Journal, Volume 1, No. 2, October, 1969. 148. Yu, J.C. Delineator Effectiveness for Highway Median Visibility. Traffic Engineering and Control, Volume 11, No. 11, March, 1970. 149. Yu, J.C. Median Visibility Improvements: Needs, Methods, and Trends. HRB Record 366, 1971. 150. Yu, J.C. and A. C. Arnn. Roadside Delineation Concepts: A National Study. HRB Record 440, 1973.

NCHRP REPORTS

4 7. Accident Rates as Related to Design Elements of Rural Highways, 1966. 53. Multiple Use of Lands Within Highway Rights-of-Way, 1967. 54. Location, Selection and Maintenance of Highway Guardrails and Median, 1968. 60. Effects of Illumination on Operating Character­istics of Freeways, 196 6. 68. Application of Vehicle Operating Character­istics to Geometric Design and Traffic Operation, 1967.

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79. Development of Improved Methods for Reduc-tion of Traffic Accidents, 1968. 93. Guidelines for Medial and Marginal Access Control on Major Highways, 196 9. 99. Visual Requirements in Night Driving, 1967. 115. Guardrail Performance and Design, 1971. 118. Location, Selection and Maintenance of Highway Traffic Barriers, 1971. 129. Guardrail Crash Test Evaluation - New Con­cepts and End Design, 1972. 137. Roadside Development: Evaluation of Research, 1972. 145. Improving Traffic Operations and Safety at Exit Core Areas, 1973. 148. Roadside Safety Improvement Programs on Freeways: A Cost-Effectiveness Priority Approach, 1974. 162. Methods for Evaluating Highway Safety Improvements, 1975.

TERM INDEX (Keyed to Bibliography)

Accidents - 4, 9, 13, 17, 18, 24, 33, 34, 36, 47, 48, 54, 60, 61, 62, 70, 78, 79, 80, 87, 93,119, 144, 147 Alcohol , drugs - 8 5 Anti-glare screen -19, 26, 27, 59, 92 Barriers -37, 44, 51, 52, 53, 57, 58, 72, 75, 82, 83, 91, 98, 99, 100, 114, 128, 137 Breakaway signs - 31, 32, 88, 102, 103, 107, 118 Channelization - 109, 110 Color and safety - 77 Cross-section -15, 28, 55, 74, 124, 125, 126, 139, 140, 141 Curves - 106 Delineation - 38, 39, 40, 66, 71, 93,109,147, 148, 149, 150 Encroachments - 49, 61, 62, 63, 77, 96 General-1, 2, 89,104 Geometry & design - 5, 16 25, 42, 55, SB, 60, 73, 74, 78, 79, 86, 90, 91, 122, 123, 125, 134, 136, 13 7, 142 Guardrail - 3, 12,29, 50, 51, 57, 113, 132, 133 Headlights - 43, 107 Illumination - 26, 38, 39, 67, 88, 94,101,108, lll, 118, 131 Longitudinal control - 2 0, 3 8, 72 Median accidents -10, 11, 22, 24, 43, 44, 45, 46, 61, 62, 63, 64, 65, 76, 130, 146 Design - 2 3 , 4 2 , 4 3 , 4 4 , 4 8 , 5 5 , 5 6 , 6 4 , 6 5 , 6 9 , 76, 90, 95, 97, 113, 145, Driver behavior - 10, Bl, 113 Mental illness - 33 Road surface - 112 Roadside furniture -14, 34, 35, 66, 67, 83, 97, 123, 124, 127, 134, 135, 138, 143, 144 Rural highways - 1, 79, 106, 116 Safety - Bl, 86, 87, 129, 142, 143, 144 Safety grates - 74 Side slopes &ditches -139, 140,141 Single vehicle accidents - 6, 7, 8, 60, 78, 85, 96, 104, 119, 120, 121 Structures - 68, 83, 84, 117 Visibility - 39, 40, 41, 105, 115, 147, 148, 149, 150

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This synthesis of current knowledge of operational effects of secondary stopping and recovery areas is based upon reported research and has been synthesized by Subcommittee III of Committee A3E02, Operational Effects of Geometrics.

A special acknowledgement is extended to Robert Coleman of the Pennsylvania Department of Transportation for his long-time service as Chairman of this subcommittee and for his efforts in initiating this report.

Subcommittee members: Thomas E. Mulinazzi, Chairman; Vasant H. Surti; Jason C. Yu; and J. Glenn Ebersole.

SPONSORSHIP OF THIS CIRCULAR

GROUP 3--OPERATION AND MAINTENANCE OF TRANSPORTATION FACILITIES Adolf D. May, Jr. , University of California, Berkeley, chairman

Committee on Operational Effects of Geometrics Stanley R. Byington, Federal Highway Administration, chairman Robert B. Helland, Federal Highway Administration, secretary Frank E. Barker, J. Glenn Ebersole, Jr. , Julie Anna Fee, John M. Feola, John C. Glennon, George F. Hagenauer, John W. Hutchinson, Rajendra Jain, Janis H. Lacis, William A. McConnell, Woodrow L. Moore, Jr., 'l'homas E. Mulinazzi, H, Douglas Robertson, NeilonJ. Rowan, Sheldon Schumacher, James J. Schuster, Robert B. Shaw, Vasant H. Surti, Jason C. Yu

K. B. Johns, Transportation Research Board staff