S21_safety Impacts Of Various Countermeasures_ltc2013.pdf

Safety Impacts of Various Crash Countermeasures Xiaoduan Sun UL Lafayette February 19, 2013 2013 Louisiana Transportation Conference

Outline • Crash Countermeasures • Converting urban undivided 4-lane roadway to five-lane roadway • Edgeline on narrow rural 2-lane highways • Raised pavement markers

Crash Countermeasures • Eliminating all crash contributing factors Pre-Event

Human

Vehicle

Environment

Event Post-Event

Haddon Matrix- a useful framework for thinking about the complexities of a crash

Human Factors (95%)

Road Environment Factors (28%) Keep in mind that everything we do must accommodate humans’ needs and match vehicles' capability

4%

24% 4% 4%

Vehicle Factors (8%) Based on Interactive Highway Safety Design Model: by Harry Lum and Jerry A. Reagan

67%

Eliminating crash contributing factors with crash countermeasures Crash is not an accident, it is preventable. Crash reduction can not happen by chance

Source: Safer Roads: A Guide to Road Safety Engineering. K.W. Ogden. Ashgate

CMF from HSM Chapter in HSM Part D

Content

# of Crash # of CMFs Countermeasures Proven to be with Known Safety effective Effect

# of Crash Countermeasures with Unknown Safety Effect

13 14 15

Roadway Segments Intersections Interchange

36 24 4

43 27 8

72 84 25

16

Special Facilities and Geometric Situations

5

16

68

Road Network Total

3 72

16 110

5 254

17

Developing CMF for Louisiana • While the majority of crash countermeasures would be the same as the once used by other states, a few countermeasures will be unique in Louisiana • Introducing few CMFs tailed to the unique situation in the state is the objective of this presentation

Outline • Crash Countermeasures • Converting urban undivided 4-lane roadway to five-lane roadway • Edgeline on narrow rural 2-lane highways • Raised pavement markers

Urban undivided multilane highways consistently exhibit low safety performance in the U.S. Representative Accident Rates by Location and Type of Road Injury Total Fatal Accidents Accidents Accidents Number per Number per Number per RURAL MVM MVM MVM 2 Lanes 0.07 0.94 2.39 4 or more lanes, divided subtotal 0.063 0.77 2.09 Freeway 0.025 0.27 0.79 URBAN 2 Lanes 0.045 1.51 4.94 4 or more lanes, undivided 0.04 2.12 6.65 4 or more lanes, divided 0.027 1.65 4.86 Freeway 0.012 0.4 1.43 9

– 1,530 miles of undivided multilane roadways under LADOTD system. 93% these roadways are in urban and suburban areas

10

Solutions? • Expensive solution: installing physical separation either by barrier or by green space (boulevard) has been the most recommended crash countermeasure for the problem

11

Solutions? • Inexpensive option: with sufficient pavement width, a four-lane undivided highway can also be easily changed to a five-lane roadway with the center lane for left-turns, which expectedly reduces rear-end collisions.

12

The five-lane design alternative including a center TWLTL in the median has, in the past 20 years, become a very common multilane design alternative for upgrading urban arterials. This design alternative has two through lanes of travel in each direction and a center TWLTL to provide for left-turn maneuvers at driveways and minor intersections. The total roadway width for a five-lane TWLTL section on an urban arterial ranges from 48 ft to 72 ft depending on the lane widths employed. From NCHRP 330, 1990

13

Pros and Cons of Two Options • Physical barrier – Better traffic (motorized or non-motorized) management – Expensive

• Five lane – Inexpensive with sufficient ROW – Not recommended for new road in Louisiana

14

However • Under the current budgetary situation, the expensive option is not financially feasible • Going with the inexpensive but not perfect solution to reduce the crashes has been one option for the situation • Several roadway segments in various LADOTD districts have implemented this inexpensive crash countermeasure in the past 15

Four segments selected for the analysis Installation Length (mi) Year

Estimated # of Driveways

Location

District

Control Section

LA 3025

D3

828-23

1.228

2003

45

Lafayette

LA 182

D3

032-02

1

2007

50

Opelousas

LA 28

D8

074-01

0.92

2005

45

Alexandria

LA 1138

D7

810-06

1.07

1999

50

Lake Charles

16

Roadway Configuration LA3025

17

LA 3025 (from 2012 Google Earth)

18

LA182

19

LA182 (from 2012 Google Earth)

20

LA1138

(from 2012 Google Earth) LA28

21

Summary of Crashes (3 years before and after) Before

Crashes

After

Percentage Change

Average Average Crash Crashes Crash Rate Rate

Crashes

Crash Rate

LA3025

358

10.05

147

4.59

-59%

-54%

LA182

178

8.12

85

3.53

-52%

-51%

LA28

206

7.38

99

4.09

-52%

-45%

LA1138

260

16.01

167

10.63

-36%

-34%

22

He a Le d-On ft Tu Le rnft e T Le urnft Tu f r No n-g nC Re oll Rig ar-E ht nd T Rig urn ht -h Tu rn Sid Rt. -i A es w i ngl e p e Sid ( O es w i D) p( SD ) Bla nk Ot he r

Crash Frequency

He ad Le -On ft Tu Le rn-e ft Tu rn Le -f ft Tu rn No -g nC Re oll a Rig r-E n ht d Tu rn -h Sid Rt. A es ng w le Sid ipe ( OD es wi ) pe ( SD ) Bla nk Ot he r

Crash Frequency

Changes by Crash Type

LA3025

250 200 150 100 50 0

100 80 60 40 20 0 Before Total After Total

LA182

Before Total

After Total

23

Changes by Pavement Surface Condition LA3025

LA182

300

180

After Total

150 100

140

Crash Frequency

Before Total

200

After Total

120 100 80 60 40

50

20

0

0 Dry

Wet

Dry

Pavement Surface Condition

160 140 120 100 80 60 40 20 0

Wet

Pavement Surface Condition

LA1138

LA28

Before Total

250

Before Total

Crash Frequency

Crash Frequency

Crash Frequency

Before Total

160

250

After Total

200

After Total

150 100 50 0

Dry

Wet

Pavement Surface Condition

Dry

Wet

Pavement Surface Condition

24

Changes by Time of the Day LA 182

LA 3025 120

200

Crash Frequency

Crash Frequency

100

Before Total

160

After Total

120 80 40

80

Before Total

60

After Total

40 20

0

0 6am12pm

12pm6pm

6pm12am

12am6am

6am12pm

LA 28

6pm12am

12am6am

LA 1138

120

160

100

Before Total

80

Crash Frequency

Crash Frequency

12pm6pm

After Total

60

40

140

Before Total

120

After Total

100 80 60 40

20 20 0

0 6am12pm

12pm6pm

6pm12am

12am6am

6am12pm

12pm6pm

6pm12am

12am6am

25

Changes by Crash Severity LA3025 LA182 LA28 LA1138 Crashes by % % % % Before After Before After Before After Before After Severity Change Change Change Change Total

358

147

-58.90%

178

85

-52.30% 206

99

-51.94% 260

167

-35.77%

PDO

277

105

-62.10%

124

63

-49.20% 148

76

-48.68% 172

119

-30.81%

Injury Crashes

81

40

-50.60%

54

22

-59.30%

58

23

-60.34%

88

48

-45.45%

Fatal

0

2

increase

0

0

0%

0

0

0%

0

0

0%

26

Benefit/Cost Ratio • Benefit—saving from reduced crashes • Cost – striping LA 3025 LA 182 LA 28 Severity Reduction Reduction Reduction Level • B/C=166! PDO 172 61 72 Injury

41

32

35

Segment

Total Benefits ($)

Total Cost ($)

B/C Ratio

LA 3025

2,753,868

14,100

195

LA 182

1,913,808

11,500

166

LA 28

2,110,212

10,600

199

LA 1138

2,317,488

12,300

188

LA 1138 Reduction 53 40

27





ˆ ˆ

CMF Results Expected Crash Reduction

Standard Deviation

Estimated the CMF

Standard Deviation

LA3025

175

27.62

0.45

0.051

LA182

110

20.53

0.43

0.062

LA28

111

21.28

0.47

0.062

LA1138

87

25.42

0.65

0.075 28

What does the result mean? A certainty in crash reduction Roadway LA3025 LA182 LA28 LA1138

Estimated CMF 0.45 0.43 0.47 0.65

Standard Deviation 0.051 0.062 0.062 0.075

CMF+ 3*Standard Deviation 0.60 0.62 0.66 0.88

Probabilty Distribution

Probability Distribution

LA1138

LA3025

0.9989 0.65 CMF Value

Probability Distribution

0.88

0.45 CMF Value

29

Probability Distribution

Results Discussion • The crash reduction by the re-striping/lane conversion projects is striking and the estimated CMF is impressive (crash countermeasures, as listed in the first edition of the HSM, seldom yield CMF values smaller than 0.5) • The estimated CMF and standard deviation on all roadway segments indicate a certainty that a re-striping project reduces crashes. 30

Results Discussion • Reductions are consistent cross crash category • It is a very cost-effective crash countermeasure • Demonstrating the need for flexibility in selecting the best safety improvement project under the existing constraints (financial or otherwise). • If and when funds do become available and sufficient right-of-way (ROW) can be obtained, these two 5-lane roadway segments can be converted to a boulevard roadway type, a concept very much promoted today in urban and suburban areas in Louisiana 31

Sustainable crash reduction LA3025 Crash Frequency

3 years before 150

3 years after after

3 years after 100 50 0 2000

2001

2002

2004

2005

2006

2008

2009

2010

Year

32

3 years before

3 years after after 3 years after

Hurricane Rita

3 years after after

3 years before 3 years after

33

CMF as a function of AADT AADT vs. Estimated CMF y = 3E-09x 2 - 0.0001x + 1.8028 R2 = 0.996

0.9 0.8

CMF

0.7 0.6 0.5 0.4 0.3 0.2 10,000

15,000

20,000

25,000

30,000

AADT

34

Due to the huge success of the lane-conversion project, more segments from LADOTD District 3 have been recently re-striped:

• • • • •

LA 14-Bypass in Abbeville LA 14 in Abbeville US 190 in Eunice LA 93 in Sunset LA 14 in New Iberia

35

Acknowledgement • • • •

Mr. Nick Fruge from District 3 Ms. Bridget Webster from District 8 Mr. Jason Roberson from District 4 Mr. Tyson Thevis from District 7

Outline • Project background • Converting urban undivided 4-lane roadway to five-lane roadway • Raised pavement markers • Edgeline on narrow rural 2-lane highways

• Raised pavement markers (delineation purpose)

The need to have Louisiana CMF on Raised Pavement Markers (RPM) CMF from the HSM

Setting (Road Type)

Traffic Volume (AADT) ≤ 20,000 Rural 20,001-60,000 (Four-lane Freeways) >60,000

Crash Type (Severity) Nightime All Types (All Severities)

CMF Std. Error 1.13 0.2 0.94 0.3 0.67 0.3

Ref: Bahar, G., C. Mollett, B. Persaud, C. Lyon, A. Smiley, T. Smahel, and H. McGee. National Cooperative Highway Research Report 518: Safety Evaluation of Permanent Raised Pavement Markers. NCHRP, Transportation Research Board, National Research Council, Washington, DC, 2004.

Should the state continue the practice?

Developing CMF for RPM • Data – Annual RPM and striping ratings – Crash

• Analysis – By setting (urban vs. rural) – By time (nighttime vs. daytime)

Ratings • Three condition ratings: – – –

‘G’ as Good ‘P’ as Poor ‘F’ as Fair

• Rating ‘C’ as Construction 2002

2003

2004

2005

2006

2007

2008

2009

2010

Control Section

Section Length

450-91

2.54

G

G

P

G

G

F

F

F

P

450-92

1.36

F

F

G

G

G

F

F

F

P

450-93

3.40

F

F

G

G

G

F

F

F

P

450-94

1.17

F

F

G

G

G

F

F

F

P

450-95

0.13

F

F

G

G

G

F

F

F

P

450-96

0.38

F

F

G

G

G

F

F

F

P

Summary Number of Segments in Each Rating Group in Nine years

Freeway GG

GF

GP

FG

FF

FP

PG

PF

PP

Rural

606

85

171

63

110

140

75

31

285

Urban

1,028

189

280

156

214

266

141

88

734

Total

1,634

274

451

219

324

406

216

119

1,019

Average Crash Rate by Combined Ratings on Rural freeways Rural and night hours

Rural and 24 hours 0.8 0.7

0.760

0.25

0.817

0.666

Avg. Crash Rate

Avg. Crash Rate

0.9

0.6 0.5 0.4 0.3 0.2 0.1

0.196

0.2 0.159

0.163

GG

FF

0.15 0.1 0.05 0

0 GG

FF

Striping and RPM rating

23% increase

PP

Striping and RPM rating

23% increase

PP

Average Crash Rate by Combined Ratings on Urban freeways

Urban and Night hours

Urban and 24 hours 2.5

0.5 2.005

2.077

2

Avg. Crash Rate

Avg. Crash Rate

2.113

1.5 1 0.5 0

0.4

0.384

0.406

0.369

0.3 0.2 0.1 0

GG

FF

Striping and RPM rating

PP

GG

FF

Striping and RPM rating

PP

Average crash rate by single rating on rural freeways Rural and 24 hours

Rural and 24 hours 0.9

0.9 0.675

0.7

0.724

0.760

0.8

Avg. Crash Rate

Avg. Crash Rate

0.8 0.6 0.5 0.4 0.3 0.2

0.692

0.706

F

P

0.6 0.5 0.4 0.3 0.2 0

0 G

F

G

P

Striping rating

RPM rating

Rural and night hours

Rural and night hours

0.25

RPM

0.25

0.2

0.180

0.178

0.161

0.2

Avg. Crash Rate

Avg. Crash Rate

0.658

0.1

0.1

Striping

0.7

0.15 0.1 0.05

0.152

0.165

0.168

F

P

0.15 0.1 0.05

0

0 G

F

Striping rating

P

G

RPM rating

Results of Statistical Test (Average Crash Rate between Good and Poor) t-test for Equality of Means Roadway Type

Feature

Crash Rate at

t

df

Mean Difference

Std. Error Difference

95% Confidence Interval of the Difference Lower

Upper

AADT ≤ 20,000 Rural

RPM

Night

-1.781

489

-0.033

0.018

-0.069

0.003

Rural Rural Rural

RPM RPM+Striping RPM+Striping

24 Hrs Night 24 Hrs

-1.101 -2.603 -2.591

489 309 309

-0.065 -0.063 -0.212

0.059 0.024 0.082

-0.181 -0.110 -0.373

0.051 -0.015 -0.051

RPM

Night

-2.665

816

-0.038

0.014

-0.066

-0.010

RPM RPM+Striping RPM+Striping

24 Hrs Night 24 Hrs

-3.249

816

-0.142

0.044

-0.228

-0.056

-2.285 -2.840

492 492

-0.047 -0.168

0.020 0.059

-0.087 -0.284

-0.007 -0.052

Rural

RPM

Night

-2.128

1339

-0.025

0.012

-0.049

-0.002

Rural

RPM

24 Hrs

-2.573

1339

-0.102

0.040

-0.180

-0.024

Rural

RPM+Striping

Night

-2.800

889

-0.045

0.016

-0.077

-0.013

Rural

RPM+Striping

24 Hrs

-3.504

889

-0.186

0.053

-0.289

-0.082

20,000≤AADT ≤ 60,000 Rural Rural Rural Rural AADT ≤ 60,000

CMF Development • • •

Crash rate is used for the analysis Only “Good’’ ratings and “Poor” ratings are considered Nine years data is used for both ratings

Highway Type

Feature

Crash Hour

Rating

N

Mean

CMF

RPM

Night

Good

291

0.139

0.81

Poor

200

0.172

Good

291

0.635

Poor

200

0.7

Good

225

0.138

Poor

86

0.201

Good

225

0.644

Poor

86

0.856

Good

436

0.141

Poor

382

0.179

Good

436

0.596

Poor

382

0.738

Good

329

0.148

Poor

165

0.195

Good

329

0.602

Poor

165

0.77

Good

745

0.153

Poor

596

0.178

Good

745

0.655

Poor

596

0.757

Good

606

0.155

Poor

285

0.2

Good

606

0.655

Poor

285

0.841

AADT≤ 20,000 Rural Rural Rural Rural

RPM RPM+Striping RPM+Striping

24 Hrs Night 24 Hrs

0.91 0.69 0.75

20,000 ≤ AADT≤ 60,000 Rural

RPM

Rural Rural Rural

RPM RPM+Striping RPM+Striping

Night 24 Hrs Night 24 Hrs

0.79 0.81 0.76 0.78

AADT≤ 60,000 Rural Rural Rural Rural

RPM RPM RPM+Striping RPM+Striping

Night 24 Hrs Night 24 Hrs

0.86 0.87 0.78 0.78

Results Discussion • RPM does offer safety benefit to the state rural freeways based on all analysis methods • Because of combined effects of two ratings, it is hard, if not impossible, to accurately estimate CMF for RPM • It is conservative to say CMF on RPM is about 0.90 • No safety benefit of RPM is detected on urban freeways

Outline • Project background • Converting urban undivided 4-lane roadway to five-lane roadway • Raised pavement markers • Edgeline on narrow rural 2-lane highways

Edgeline Requirement

Road Width AADT

Previous MUTCD (1994)

Updated MUTCD (2000)1

Current LaDOTD Policy (1994)2

No Requirement

20-ft or Wider

22-ft or Wider

No Requirement

Greater than 3,000

No Requirement

Research Investigation • The 2007 study on 10 segments of narrow rural 2-lane highways proved that: – With the edge line, vehicles tend to move away from the road edge; thus, the risk of having a running-offroadway crash is likely to be reduced – The implementation of edge lines is likely to reduce the head-on and sideswipe collisions at night because of the reduced number of vehicles crossing the centerline in the nighttime.

• The impact of edge line on crashes is also investigated on the selected segments from all LaDOTD districts

after before

Control Section (District 3)

Highway Number Log from and to

Suggestion Mile post (Log Mile)

823-27

0087 0-1.89

Starting at milepost 4.0 for 3 miles (0.25 mile before the control section)

• 389-01 after before

Control Section (D3)

Highway Number Log from and to

Suggestion Milepost (Log Mile)

389-01

0098 2.59-7.15

Starting at milepost 27 for 6 miles (log-mile 2 for 6 miles)

after before

Control Section (D4)

Highway Number Log from and to

Suggestion Milepost (Log Mile)

048-02

0169 4.72-8.29

Starting at milepost 22 for 5 miles (log mile 4.5 for 5 miles)

• Crash data analysis • Three years before and three years after

2005 2006 2007 Before

2008

2009

Installation Year

2010 2011 After

Total Crashes 2005

2006

2007

2009

2010

2011

DOTD District

Total

Total

Total

Total

Total

Total

2

23

34

24

19

8

17

3

86

68

67

81

85

68

4

12

16

8

12

5

6

5

84

74

85

90

99

72

7

21

30

14

10

14

17

8

16

13

15

10

14

10

58

5

3

4

2

4

1

61

32

36

17

15

15

20

62

85

103

83

71

62

63

Total

345

346

295

290

299

263

Results Before 3 Years- After 3 Years

Naïve B-A Method 2

Improved Prediction

DOTD District (No. of CSECT)

Reduction in Crashes

Index of Effectiveness

Reduction in Crashes

Index of Effectiveness

2 (1) 3 (9) 4 (2) 5 (4) 7 (2) 8 (2) 58 (1) 61 (3) 62 (4)

4 -13 13 -18 24 9 5 35 75

0.58 1.05 0.62 1.07 0.62 0.77 0.54 0.58 0.72

10 -17 18 1 14 13 2 44 108

0.38 1.07 0.54 0.99 0.72 0.69 0.69 0.52 0.64

Results Before 3 Years- After 3 Years

Improved Prediction Method Estimated Expected Reduction

Stdev.

CMF

Stdev.

194

48

0.81

0.041

Result Interpretation

  2

0.701

0.868

1.0278

Benefit-Cost Analysis Severity Type

2004-2007 (Before Years)

2009-2011 (After Years)

Change

Fatal

12

13

-1

4,376,304

-4,376,304

Injury

424

341

83

71,139

5,904,537

PDO

550

498

52

3,292

171,184

Total Benefit

1,699,417

All Control Sections

Including Loss Safety of Benefit ($) Quality of Life

Cost ($0.15 per foot)

Benefit

B-C Ratio

86,835

1,699,417

19.57

Putting together •

Our Analysis

0.81

Safety Trend for the Narrow Rural 2-lane

-5.6%

Final Estimated CMF

0.87

HSM CMF for Rural Two Lane

Source: Highway Safety Manual (1st Edition), Vol. 3, 2010

Results Discussion • Implementing edge line is most likely to reduce number of crashes based on our crash analysis • The expected reduction is estimated 13%

Summary A very effective short-term crash countermeasure for urban undivided 4-lane roadway

Reducing crashes on rural freeway

Results in lower crash rate

Thank You and Questions?