University of Minnesota Intersection Decision Support Research - Results of Crash Analysis

University of Minnesota Intersection Decision Support Research

-Results of Crash Analysis

University of Minnesota Intersection Decision Support Research

-Results of Crash Analysis

Presented at

IDS Quarterly Review

January 15, 2004

Agenda

• Deployment Opportunities • Rural Roadway Safety Issues• Rural Intersection Safety Issues• Candidate Intersections for the IDS

Research Modeling• Conclusions

Page 2

Concept of “Critical Crash Rate”

Source: Traffic Safety Fundamentals Handbook

Page 3

PotentialDeployment Opportunities

• Initial Thoughts About Deployment

– Highest Priority: 2-Lane & Expressway thru-STOP intersections with crash rate greater than critical crash rate.

– How Many Intersections in the State Highway System? Total >CR (% of total)

• 2-Lane - 3,388 | 104 (~ 3%)• Expressway - 396 | 23 (~ 6%)

Page 4

Statewide Crashes: - Statewide: 117,151 - Rural: 46,998 - Expressway: 10,996 - Intersection: 4,231 - Fatal: 70 - “A” Injury: 143 - 2-Lane: 23,179 - Intersection: 6,838 - Fatal: 121 - “A” Injury: 237


Statewide Fatal Crashes590

State Highway System - 287 fatal crashes - 11,900 miles of road - 33 Billion VMT

County and Local Roads - 303 fatal crashes - 123,400 miles of road - 22 Billion VMT

Urban83

Rural204

Urban82

Rural221

Segment &Other TCD*

~ 150

Thru-STOP*~ 45

Signalized*~ 9

Segment &Other TCD*

~ 162

Thru-STOP*~ 49

Signalized*~ 10

Expressway*18

Expressway*8

2-Lane*26 Source: Mn/DOT 2002 Crash Data

Page 10

* NOTE: Number of Crashes Estimated


Selection Criteria: - State Highway System - Rural - Thru-Stop - 2000 to 2002 Crash Records

Intersections with2 Fatal Crashes

7

Expressway 5

Two-Lane2

Crash Rate > Critical 4

Crash Rate > Critical 2

Crash Rate < Critical 1

Crash Rate < Critical 0

Page 11

Rural Roadway Segment Crash and Fatality Rates by Facility Type

1.0

1.2

0.9

0.6

1.6

1.2

0.7

1.2

1.4

0.8

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2-Lane 4-Lane Undivided 4-Lane Divided Arterial 4- & 6-Lane DividedExpressway

Freeway

Rural Facility Type

Ex

pe

cte

d R

ate

Crash Rate (per MVM)

Fatality Rate (per 100MVM)

Differences in Roadway Type

56 mi. 94 mi. 840 mi. 817 mi.8,887 mi.

Source: Mn/DOT 2000-2002 Crash Data

Page 12

September 23, 2003

Crash, Severity, and Fatality RateS of Rural Expressways by Volume

1.6

2.6

1.0

0.8

0.9

1.3

1.9

0.8

1.4

0

0.5

1

1.5

2

2.5

3

Low (ADT < 11,000 vpd) Moderate (11,000 < ADT < 28,000vpd)

High (ADT > 28,000 vpd)

Volume Group

Ra

tes

Crash Rate (per MVM)

Severity Rate (per MVM)

Fatality Rate (per 100MVM)

Effect of Volume on Rural Expressway Crash Rates

NOTE:

Both crash rate and severity rate are seen to increase as the volume increases.

Unlike the crash and severity rate, the fatality rate decreases as the roadway volume increases.

Similar to the crash rate and severity rate, the percent of intersection related crashes increases with volumes.

1Crashes occurring in interchange areas and also at intersections, alleys and driveways.

Source: Mn/DOT TH 52 Road Safety Audit

Page 13

September 23, 2003Severity Weighting: - Fatal = 5 - “A” Injury = 4 - “B” Injury = 3 - “C” Injury = 2 - PDO = 1

Intersection Crash& Severity Rates

Crash and Severity Rates for Rural Thru-STOP Intersections

0.4

0.6

0.4

1.8

0.8

1.6

0.7

0.9

0

0.4

0.8

1.2

1.6

2

Crash Rate Severity Rate

Ra

tes

Rural Thru-STOPRural Expressway Thru-STOP (198)Rural Expressway Thru-STOP - Over Critical Crash Rate (23)US 52 RSA - Thru-STOP Over Critical Crash Rate (8)

NOTE:

Rural expressway thru-STOP intersections have similar crash and severity rates to all rural thru-STOP intersections.

The average crash rate of intersections over the critical crash rate is twice the crash rate of all rural thru-STOP intersections.

The average severity rate of intersections over the critical crash rate is three times the severity rate for all rural thru-STOP intersections.

US 52 intersections over the critical crash rate have a nearly identical crash rate and severity rate when compared to rural expressway intersections over the critical crash rate.

Page 14

September 23, 2003

Source: Rural Thru-STOP: Mn/DOT 2000 – 2002 Crash DataRural Expressway Thru-STOP: Mn/DOT 2000 – 2002 Crash DataRural Expressway Thru-STOP – Over Critical Crash Rate: Mn/DOT 2000 – 2002 Crash DataUS 52: US 52 Road Safety Audit (January 1999 – March 2002 Crash Data)

Crash Type Distribution for Rural Thru-STOP Intersections

23%

2%2%

9%7%

10%

6%

13%

5%3%

5%

28%

16%

18%17%

5% 4%

36%

14%

0.6% 0.4%

21%

4%1% 0.5%

53%

15%

1%2%

11%13%

1%

53%

0%

10%

20%

30%

40%

50%

60%

Other Rear End SideswipePassing

Left Turn RunoffRoad

Right Angle Headon SideswipeOpposing

Right Turn

Crash Type

Pe

rce

nta

ge

Rural Thru-STOPRural Expressway Thru-STOP (396)Rural Expressway Thru-STOP - Over Critical Crash Rate (23)US 52 RSA - Thru-STOP Over Critical Crash Rate (8)

Intersection CrashType Distribution

NOTE:

Thru-STOP intersections for rural expressways have a higher percentage of right angle crashes in comparison to all rural thru-STOP intersections. Most other crash types show a decrease.

The percentage of right angle crashes significantly increases for rural expressway intersections over the critical crash rates.

US 52 intersections over the critical crash rate are nearly identical to the crash type distribution of all rural expressway intersections over the critical crash rate.

Source: Rural Thru-STOP: Mn/DOT 2000 – 2002 Crash DataRural Expressway Thru-STOP: Mn/DOT 2000 – 2002 Crash DataRural Expressway Thru-STOP – Over Critical Crash Rate: Mn/DOT 2000 – 2002 Crash DataUS 52: US 52 Road Safety Audit (January 1999 – March 2002 Crash Data)

Page 15

September 23, 2003

Effect of Volumeon Right Angle Crashes

NOTE:

The “Medium” and “Large” volume increments strongly show that the average number of right angle crashes increases as volumes increase.

The “Small” volume increments tend to support that right angle crashes increase with volume, but the small number of intersections in each volume category results in more fluctuations.

Source: Mn/DOT 2000 – 2002 Crash Data

Thru-STOP Intersections Over the Critical Crash Rate on Rural Expressways

5.0

7.7

18.3

10.0

5.7

15.0

3.03.4

8.39.1

11.6

10.0

0

4

8

12

16

20

0 - 5,000 5,000 -10,000

10,000 -15,000

15,000 -20,000

20,000 -25,000

25,000 -30,000

30,000 -35,000

0 -10,000

10,000 -20,000

20,000 -35,000

0 -15,000

15,000 -35,000

Entering Volume

Av

era

ge

Nu

mb

er

of

Rig

ht

An

gle

Cra

sh

es

OVERALL AVG = 8.8

Volume Ranges inSmall Increments

Volume Ranges inMedium Increments

Volume Rangesin Large

Increments

1 115135131764 12

Thru-STOP Intersections Over the Critical Crash Rate on Rural Expressways

83%

35%

50%52%

38%

44%

49%53% 53%

57%56%

48%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0 -5,000

5,000 -10,000

10,000 -15,000

15,000 -20,000

20,000 -25,000

25,000 -30,000

30,000 -35,000

0 -10,000

10,000 -20,000

20,000 -35,000

0 -15,000

15,000 -35,000

Entering Volume Ranges

Ave

rag

e P

erc

en

tag

e o

f Rig

ht A

ng

le C

rash

es

OVERALL AVG = 50%

1 115135131764 12

Volume Ranges inSmall Increments

Volume Ranges inMedium Increments

Volume Rangesin Large

Increments

Page 16

September 23, 2003

September 23, 2003

Severity for Rural Thru-STOP Intersections

3%

23% 23%

2% 3%

19%

60%

45%

5%

16%

0%

10%

20%

30%

40%

50%

60%

70%

Fatal Severe Injury Moderate Injury Minor Injury Property DamageOnly

Crash Severity

Pe

rce

nt

of

Cra

sh

es

Right Angle

All Crashes

Severity of Right Angle Crashes

NOTE:

The percent of right angle crashes at rural, thru-STOP intersections that result in a fatality is approximately twice that for all rural, thru-STOP intersection crashes.

Right angle crashes are also more likely to result in an injury crash.


Page 17

September 23, 2003

(A) (B) (C)

Will Signal WarrantsBe Met on Expressways?

Of the 23 Rural Expressway Intersections Over Of the 23 Rural Expressway Intersections Over the Critical Crash Rate:the Critical Crash Rate: - 2 expected to meet Warrant 1A and 4 expected - 2 expected to meet Warrant 1A and 4 expected to meet Warrant 1B.to meet Warrant 1B. - If the 30% volume reduction used, then 6- If the 30% volume reduction used, then 6 expected to meet Warrant 1A and 9 expected toexpected to meet Warrant 1A and 9 expected to meet Warrant 1B.meet Warrant 1B.

0

5000

10000

15000

20000

25000

30000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Minor StreetAPPROACH VOLUME

Maj

or

Str

eet

AV

ER

AG

E D

AIL

Y T

RA

FF

IC (

AD

T)

** A major street ADT and minor street approach volume falling in this range, will not warrant a traffic signal under Warrant 1A (95% confidence level).

NOTE: A major street ADT and minor street approach volume falling outside of the indicated regions indicates hourly approach volumes will be needed to draw any conclusions whether the signal is or is not warranted under Warrant 1.

If No Volume Reduction Used

1 Lane &2 Lanes or More

SIGNAL WARRANT ANALYSISWarrant 1A - Minimum Vehicular Volume

* A major street ADT and minor street approach volume falling in this range, will likely warrant a traffic signal under Warrant 1A (95% confidence level).

If 30% Volume Reduction Used

WarrantNot Met**

WarrantMet*

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Minor StreetApproach Volume

Maj

or

Str

eet

Ave

rag

e D

aily

Tra

ffic

SIGNAL WARRANT ANALYSISWarrant 1B - Interruption of Continuous Traffic


1 Lane &2 Lanes or More





WarrantNot Met**

WarrantMet*

Page 5

Will Signal WarrantsBe Met on 2-Lane Roads?

Page 6

Of the 104 Rural 2-Lane Intersections Over the Of the 104 Rural 2-Lane Intersections Over the Critical Crash Rate:Critical Crash Rate: - 1 expected to meet Warrant 1A and 2 expected - 1 expected to meet Warrant 1A and 2 expected to meet Warrant 1B.to meet Warrant 1B. - If the 30% volume reduction used, then 6- If the 30% volume reduction used, then 6 expected to meet Warrant 1A and 5 expected toexpected to meet Warrant 1A and 5 expected to meet Warrant 1B.meet Warrant 1B.

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500

Minor StreetAPPROACH VOLUME

Maj

or

Str

eet

AV

ER

AG

E D

AIL

Y T

RA

FF

IC (

AD

T)




1 Lane &1 Lane

SIGNAL WARRANT ANALYSISWarrant 1A - Minimum Vehicular Volume



WarrantNot Met**

WarrantMet*

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500

Minor StreetApproach Volume

Maj

or

Str

eet

Ave

rag

e D

aily

Tra

ffic

SIGNAL WARRANT ANALYSISWarrant 1B - Interruption of Continuous Traffic


1 Lane &1 Lane





WarrantNot Met**

WarrantMet*

Page 7

Source: Traffic Safety Fundamentals Handbook

Page 8

HIGHLIGHTS:

• Traditionally the installation of a traffic signal was expected to result in an increase in total and rear end crashes and a decrease in right angle crashes and severity.

• Before vs. After studies of traffic signal installations along TH 52 and TH 14 generally indicate similar trends:

Total crashes, PDO crashes and rear end crashes increased.

Right angle and fatal crashes were reduced.

The number of injury crashes remained about the same.

• The project in Byron also illustrated the crash rate regressing to the mean for similar signalized intersections.

Typical Results ofTraffic Signal Installation

TH 14 in Byron, MN

10

4

6

0

8

0

6

0

4

8

0.3

9

15

0.8

0

2

4

6

8

10

12

14

16

Total PDO Injury Fatal Right Angle Rear End RateCrashes

Num

ber

of C

rashes

Before

After

TH 52 in Cannon Falls, MN

14

4

2423

13

35

17

2 0.80

10

36

12

0.90

5

10

15

20

25

30

35

40

Total PDO Injury Fatal Right Angle Rear End Rate

Crashes

Num

ber

of C

rashes Before

After

Case Study:Change in Intersection Delay

749.5

2754.0

568.7

13631

0

2000

4000

6000

8000

10000

12000

14000

16000

To

tal

Del

ay (

Sec

on

ds) Major Street Delay

Minor Street Delay

Comparison of TOTAL PM Peak Hour DelaySource: Mn/DOT Peak Hour Turning Movements using Highway Capacity Software

Through / STOP Control Traffic Signal Control

Page 9

Source: TH 244 / Wedgewood Drive Signal Analysis (Mahtomedi, MN); Howard R. Green Company

Rural Expressway IntersectionsOver the Critical Rate

Intersection of:

EnteringADT

Number ofCrashes

Fatal + “A”Injury

CrashesCrashRate

CriticalCrashRate

SeverityRate Right Angle

Crashes

US 2 CSAH 41 4,190 6 0 1.3 0.8 2.4 5 (83%)US 2 CSAH 9 14,610 12 1 0.7 0.6 1.1 3 (25%)US 2 CSAH 11 16,710 16 2 0.9 0.6 1.5 5 (31%)US 10 CSAH 8 15,690 15 2 0.9 0.6 1.7 6 (40%)US 10 CR 43 18,450 18 1 0.9 0.6 1.9 11 (61%)US 52 CSAH 141 28,790 46 4 1.5 0.6 2.9 32 (70%)US 52 TH 57 17,770 14 1 0.7 0.6 1.5 7 (50%)US 52 CSAH 9 17,990 20 1 1.0 0.6 2.4 13 (65%)US 52 CSAH 86 21,320 18 0 0.8 0.6 1.5 10 (56%)US 52 CSAH 472 27,380 24 4 0.8 0.6 1.9 15 (63%)US 52 CSAH 483 30,220 26 3 0.8 0.6 1.6 10 (38%)US 53 CSAH 52 9,820 9 1 0.8 0.7 1.8 5 (56%)US 61 Orrin Street (Winona) 17,490 20 1 1.0 0.6 1.6 14 (70%)US 71 CSAH 52 11,870 18 1 1.4 0.7 2.2 12 (67%)US 169 CSAH 11 10,940 13 1 1.2 0.7 2.5 10 (77%)US 169 CSAH 21 13,310 12 0 0.8 0.6 1.6 4 (33%)US 212 TH 5/25 (W. Jct) 12,170 12 0 0.9 0.6 1.6 6 (50%)MN 5 Granada Avenue (Oakdale) 14,120 22 1 1.4 0.6 2.5 11 (50%)MN 5 CSAH 6 15,950 16 0 0.9 0.6 1.5 8 (50%)MN 13 TH 19 7,960 8 0 0.9 0.7 1.8 3 (38%)MN 23 CSAH 7 7,910 9 1 1.0 0.7 2.7 3 (33%)MN 60 CR 118 8,380 8 0 0.9 0.7 1.3 1 (13%)MN 65 177th Avenue (Ham Lake) 28,370 21 2 0.7 0.6 1.3 8 (38%)


Page 18

September 23, 2003

Evaluating Criteria:• High Crash Rate• High Frequency of Crashes• High Percentage of RA Crashes

1Intersection is being replaced with an interchange as part of US 52 Design-Build.

2An overpass is programmed for construction in FY 2004.

3Intersection located in influence area for a new signal installed at CSAH 46.

Candidate Intersections - Summary Table

Page 19

September 23, 2003

Age of At-Fault Drivers Involved in Crossing Path Crashes

33%

58%

8%13%

53%

33%

18%

82%

5%

16%

72%

7%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Young (< 20) Middle (20 - 64) Old (> 64) Unknown

Age of At-Fault Driver

Pe

rce

nta

ge

US 10 & CR 43 (12)

US 52 & CSAH 9 (15)

MN 65 & 177th Ave (11)

Expected

Candidate Intersections - At-Fault Driver Age


Page 20

September 23, 2003

NOTE:

Young” drivers are over represented in crashes at the intersection of US 10 & CR 43.

“Old” drivers are over represented in crashes at the intersection of US 52 & CSAH 9.

Crash Type Distribution for the Candidate Intersections

6% 6%

10%

5%

15%

65%

24%

14%

10% 10%

5%

21%

5%2% 1%

11%

61%

11%

6% 5%

38%

0.4%

14%

4%

17%

36%

0%

10%

20%

30%

40%

50%

60%

70%

Other Rear End SideswipePassing

Left Turn Run OffRoad

Right Angle Head On Sideswipe -Opposing

Right Turn

Crash Type

Per

cen

tag

eUS 10 & CR 43 (18)

US 52 & CSAH 9 (22)

MN 65 & 177th Ave (21)

Expected (396)

Candidate Intersections - Crash Type Distribution


Page 21

September 23, 2003

Candidate Intersections -Right Angle Crashes

NOTE:

Nearly 80% of right angle crashes at the candidate intersections occurred on the farside of the intersection (i.e., when vehicle on minor street is pulling out of median cross-over).

At the candidate intersections, nearly 90% of all right angle crashes were “Stopped, Pulled Out” while no “Ran the STOP” crashes were observed.


Contributing Factors

September 23, 2003

September 23, 2003

Right Angle Crash Location

Page 22

Conclusions

• There are safety issues along segments of rural roadway - crash frequencies appear to increase significantly as volume increase.

• There are safety issues at rural Thru-STOP intersections - the severity and frequency of right angle crashes are a particular concern

• Intersections with unusually high crash frequencies (greater than the critical Rate) are different than “normal” intersections - not only are there more crashes but the distribution is also different (more right angle crashes).

Page 23

Conclusions cont’d

• The primary contributing factor to right angle crashes at rural thru-STOP intersections is gap selection and this becomes more critical at higher traffic volumes (because there are fewer safe gaps to select).

• The best candidate intersection to include in the IDS research is...

Page 24

Recommended Candidate for Operational Test - US 52 & CSAH 9

CSAH 9CSAH 9

U.S. 52

U.S. 52

Page 25

US 52 & CSAH 9

NB

SB

Page 26

• Intersections has a high percentage of right angle crashes (65%).

• 33% of at-fault drivers in crossing path crashes are over the age of 64.

• US 52 corridor from Inver Grove Heights to Rochester has nearly one-quarter of rural expressway, thru-STOP intersections over the critical crash rate.

Documents

University of Minnesota Intersection Decision Support Research - Results of Crash Analysis