s21_safety impacts of various countermeasures_ltc2013

7/29/2019 S21_Safety Impacts of Various Countermeasures_LTC2013

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Safety Impacts of Various Crash

Countermeasures

Xiaoduan Sun

UL LafayetteFebruary 19, 2013

2013 Louisiana Transportation Conference


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Outline

Crash Countermeasures

Converting urban undivided 4-lane roadway to

five-lane roadway

Edgeline on narrow rural 2-lane highways

Raised pavement markers


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Eliminating all crash contributing factors

Pre-EventEvent

Post-Event

Human Vehicle Environment

Haddon Matrix- a useful framework for thinking about the

complexities of a crash


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Based on Interactive Highway Safety Design Model:

by Harry Lum and Jerry A. Reagan

Road

EnvironmentFactors (28%)

Vehicle

Factors (8%)

Human

Factors (95%)

4%

24% 67%4%

4%

Road

EnvironmentFactors (28%)

Vehicle

Factors (8%)

Human

Factors (95%)

4%

24% 67%4%

4%

4%

24% 67%4%

4%

Keep in mind thateverything we do must

accommodate humans

needs and match vehicles'

capability


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Eliminating crash contributing factors

with crash countermeasures

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

Crash is not an

accident, it is

preventable. Crash

reduction can not

happen by chance


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CMF from HSM

Chapter in

HSM Part

D

Content

# of CMFs

Proven to be

effective

# of Crash

Countermeasures

with Known Safety

Effect

# of Crash

Countermeasures with

Unknown Safety Effect

13 Roadway Segments 36 43 72

14 Intersections 24 27 84

15 Interchange 4 8 25

16Special Facilities and

Geometric Situations5 16 68

17 Road Network 3 16 5

Total 72 110 254


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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


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Outline


Converting urban undivided 4-lane

roadway to five-lane roadway Edgeline on narrow rural 2-lane highways



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9

Urban undivided multilane highways consistently

exhibit low safety performance in the U.S.

Fatal Accidents

Injury

Accidents

Total

Accidents

RURAL

Number per

MVM

Number per

MVM

Number per

MVM

2 Lanes 0.07 0.94 2.394 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


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10

1,530 miles of undivided multilane roadways

under LADOTD system. 93% these roadways are in

urban and suburban areas


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11

Solutions?

Expensive solution: installing physicalseparation either by barrier or by green

space (boulevard) has been the most

recommended crash countermeasure for

the problem


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12

Inexpensive option: with sufficient pavementwidth, 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.

Solutions?


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13

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 directionand 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


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14

Pros and Cons of Two Options

Physical barrier

Better traffic (motorized

or non-motorized)

management

Expensive

Five lane

Inexpensive with

sufficient ROW

Not recommended fornew road in Louisiana


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15

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 oneoption for the situation

Several roadway segments in various LADOTD

districts have implemented this inexpensivecrash countermeasure in the past


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16

Four segments selected for the

analysis

DistrictControl

SectionLength (mi)

Installation

Year

Estimated

# of

Driveways

Location

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


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17

Roadway Configuration

LA3025


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18

LA 3025 (from 2012 Google Earth)


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19

LA182


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20

LA182 (from 2012 Google Earth)


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21

LA1138

LA28

(from 2012 Google Earth)


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22

Summary of Crashes(3 years before and after)

Before After Percentage Change

Crashes

Average

Crash

Rate

Crashes

Average

Crash

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%


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23

Changes by Crash Type

LA182

0

20

40

60

80

100

Head

-On

Left

Turn

-e

Left

Turn

-f

Left

Turn

-g

Non

Coll

Rear

-End

Righ

tTur

n-h

Righ

tTur

n-i

Rt.A

ngle

Side

swip

e(O

D)

Side

swip

(SD)

Blan

k

Oth

er

Crash

Frequency Before

Total

After

Total

LA3025

0

50

100

150

200

250

Head-

On

Left

Turn-

e

Left

Turn-f

Left

Turn-

g

NonC

oll

Rear-E

nd

Righ

tTurn

-h

Rt.An

gle

Side

swip

e(OD)

Side

swip

e(SD)

Blank

Oth

er

Crash

Frequency Before

Total

After

Total


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24

Changes by Pavement Surface Condition

LA182

0

20

40

60

80

100

120

140

160

180

Dry Wet

Pavement Surface Condition

Crash

Frequency

Before

Total

After

Total

LA3025

0

50

100

150

200

250

300

Dry Wet


Crash

Frequency

Before

Total

After

Total

LA28

0

20

40

60

80

100

120140

160

Dry Wet


Crash

Frequency

Before

Total

After

Total

LA1138

0

50

100

150

200

250

Dry Wet


Crash

Frequency

Before

Total

After

Total


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25

Changes by Time of the Day

LA 3025

0

40

80

120

160

200

6am-

12pm

12pm-

6pm

6pm-

12am

12am-

6am

Crash

Frequency

Before

Total

After

Total

LA 182

0

20

40

60

80

100

120

6am-

12pm

12pm-

6pm

6pm-

12am

12am-

6am

Crash

Frequency

Before

Total

After

Total

LA 1138

0

20

40

60

80

100

120

140

160

6am-

12pm

12pm-

6pm

6pm-

12am

12am-

6am

Crash

Frequenc

BeforeTotal

After

Total

LA 28

0

20

40

60

80

100

120

6am-

12pm

12pm-

6pm

6pm-

12am

12am-

6am

Crash

Frequenc

Before

Total

After

Total


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26

Changes by Crash Severity

Crashes

by

Severity

LA3025 LA182 LA28 LA1138

Before After%

ChangeBefore After

%

ChangeBefore After

%

ChangeBefore After

%

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

Crashes81 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%


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27

Benefit/Cost Ratio

Benefitsaving from reduced crashes

Cost striping

B/C=166!

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 3025 LA 182 LA 28 LA 1138

Reduction Reduction Reduction Reduction

PDO 172 61 72 53

Injury 41 32 35 40

Severity

Level


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28

CMF Results

Expected

Crash

Reduction

StandardDeviation

Estimatedthe CMF

StandardDeviation

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


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29

RoadwayEstimated

CMF

Standard

Deviation

CMF+

3*Standard Deviation

LA3025 0.45 0.051 0.60

LA182 0.43 0.062 0.62

LA28 0.47 0.062 0.66

LA1138 0.65 0.075 0.88

CMF Value0.88

0.9989

0.65

Probabilty Distribution

LA1138

What does the result mean?

A certainty in crash reduction


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30

Results Discussion

The crash reduction by the re-striping/laneconversion projects is striking and theestimated CMF is impressive (crash

countermeasures, as listed in the first editionof the HSM, seldom yield CMF values smallerthan 0.5)

The estimated CMF and standard deviation onall roadway segments indicate a certainty thata re-striping project reduces crashes.


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31

Reductions are consistent cross crash category It is a very cost-effective crash countermeasure

Demonstrating the need for flexibility in selectingthe 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, aconcept very much promoted today in urban andsuburban areas in Louisiana

Results Discussion


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32

Sustainable crash reduction

LA3025

0

50

100

150

2000 2001 2002 2004 2005 2006 2008 2009 2010

Year

Crash

Frequency

3 years after

3 years before

3 years after after


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33

3 years after

3 years after

3 years after after

3 years after after

3 years before

3 years before

Hurricane Rita


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34

CMF as a function of AADT

AADT vs. Estimated CMF

y = 3E-09x2 - 0.0001x + 1.8028

R2 = 0.996

0.20.3

0.4

0.5

0.6

0.70.8

0.9

10,000 15,000 20,000 25,000 30,000

AADT

CMF


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35

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


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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


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Outline

Project background

Converting urban undivided 4-lane roadway

to five-lane roadway




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Raised pavement markers (delineationpurpose)


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Setting

(Road Type)

Traffic Volume

(AADT)

Crash Type

(Severity) CMF Std. Error

20,000 1.13 0.2

20,001-60,000 0.94 0.3

>60,000 0.67 0.3

Rural

(Four-lane Freeways)

Nightime

All Types

(All Severities)

The need to have Louisiana CMF on Raised

Pavement Markers (RPM)

Should the state continue the practice?

CMF from the HSM

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.


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Developing CMF for RPM

Data

Annual RPM and striping ratings

Crash

Analysis

By setting (urban vs. rural)

By time (nighttime vs. daytime)


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Three condition ratings: G as Good

P as Poor

F as Fair

Rating C as Construction

Ratings

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


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Summary

FreewayNumber of Segments in Each Rating Group in Nine years

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


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Average Crash Rate by Combined Ratings on

Rural freeways

Rural and night hours

0.159 0.163

0.196

0

0.05

0.1

0.15

0.2

0.25

GG FF PP

Striping and RPM rating

Avg.Crash

Rate

Rural and 24 hours

0.666

0.7600.817

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

GG FF PP


Avg.Crash

Rate

23% increase 23% increase


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Average Crash Rate by Combined Ratings on

Urban freeways

Urban and 24 hours

2.1132.005 2.077

0

0.5

1

1.5

2

2.5

GG FF PP


Avg.Crash

Rate

Urban and Night hours

0.3840.406

0.369

0

0.1

0.2

0.3

0.4

0.5

GG FF PP


Avg.Crash

Rate


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Average crash rate by single rating on rural

freeways

Rural and 24 hours

0.6580.692 0.706

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

G F P

RPM rating

Avg.Crash

Rate


0.1520.165 0.168

0

0.05

0.1

0.15

0.2

0.25

G F P

RPM rating

Avg.Crash

Rate


0.161

0.180 0.178

0

0.05

0.1

0.15

0.2

0.25

G F P

Striping rating

Avg.Crash

Rate

Rural and 24 hours

0.6750.724

0.760

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

G F P

Striping rating

Avg.Crash

Rate

StripingRPM


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Results of Statistical Test(Average Crash Rate between Good and Poor)

Roadway

TypeFeature

Crash

Rate at

t-test for Equality of Means

t dfMean

Difference

Std. Error

Difference

95% Confidence Interval of

the Difference

Lower UpperAADT 20,000

Rural RPM Night -1.781 489 -0.033 0.018 -0.069 0.003

Rural RPM 24 Hrs -1.101 489 -0.065 0.059 -0.181 0.051

Rural RPM+Striping Night -2.603 309 -0.063 0.024 -0.110 -0.015

Rural RPM+Striping 24 Hrs -2.591 309 -0.212 0.082 -0.373 -0.051

20,000AADT 60,000

Rural RPM Night -2.665 816 -0.038 0.014 -0.066 -0.010

Rural RPM 24 Hrs -3.249 816 -0.142 0.044 -0.228 -0.056



AADT 60,000

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



CMFHighway

TypeFeature

Crash

HourRating N Mean CMF


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CMF

Development

Type Hourg

AADT 20,000

Rural RPM Night Good 291 0.139 0.81

Poor 200 0.172

Rural RPM 24 Hrs Good 291 0.635 0.91

Poor

200 0.7

Rural RPM+Striping Night Good 225 0.138 0.69

Poor 86 0.201

Rural RPM+Striping 24 Hrs Good 225 0.644 0.75

Poor 86 0.856

20,000 AADT 60,000

Rural RPM Night Good 436 0.141 0.79

Poor

382 0.179


Poor 382 0.738


Poor 165 0.195

Rural RPM+Striping 24 Hrs Good 329 0.602 0.78

Poor 165 0.77

AADT 60,000Rural RPM Night Good 745 0.153 0.86

Poor 596 0.178


Poor 596 0.757


Poor 285 0.2

Rural RPM+Striping 24 Hrs Good 606 0.655 0.78Poor 285 0.841

Crash rate is used for the

analysis

Only Good ratings and Poor

ratings are considered

Nine years data is used for bothratings


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Results Discussion

RPM does offer safety benefit to the staterural freeways based on all analysis methods

Because of combined effects of two ratings, it

is hard, if not impossible, to accuratelyestimate CMF for RPM

It is conservative to say CMF on RPM is about0.90

No safety benefit of RPM is detected on urbanfreeways


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Project background

Converting urban undivided 4-lane roadway

to five-lane roadway



Outline


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Edgeline Requirement

Previous

MUTCD

(1994)

Updated

MUTCD

(2000)1

Current LaDOTD

Policy(1994)2

Road

WidthNo Requirement 20-ft or Wider 22-ft or Wider

AADT No Requirement Greater than3,000 No Requirement


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Research Investigation

The 2007 study on 10 segments of narrow rural2-lane highways proved that: With the edge line, vehicles tend to move away from

the road edge; thus, the risk of having a running-off-

roadway crash is likely to be reduced The implementation of edge lines is likely to reduce

the head-on and sideswipe collisions at night becauseof the reduced number of vehicles crossing thecenterline in the nighttime.

The impact of edge line on crashes is alsoinvestigated on the selected segments from allLaDOTD districts


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Control Section

(District 3)

Highway Number

Log from and toSuggestion

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)

before

after


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389-01

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)

before

after


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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)

before

after


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Crash data analysis

Three years before and three years after

2005 2006 2007 2008 2009 2010 2011

Before Installation Year After


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Total Crashes

2005 2006 2007 2009 2010 2011

DOTD

DistrictTotal 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 1058 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


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Results

Before 3 Years- After 3 Years

Nave 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) 4 0.58 10 0.38

3 (9) -13 1.05 -17 1.074 (2) 13 0.62 18 0.54

5 (4) -18 1.07 1 0.99

7 (2) 24 0.62 14 0.72

8 (2) 9 0.77 13 0.69

58 (1) 5 0.54 2 0.69

61 (3) 35 0.58 44 0.52

62 (4) 75 0.72 108 0.64


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Results

Before 3 Years- After 3 Years

Improved Prediction Method

Estimated

Expected

Reduction

Stdev. CMF Stdev.

194 48 0.81 0.041


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Result Interpretation

0.8680.701 1.0278

2


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Benefit-Cost Analysis

SeverityType

2004-2007

(Before

Years)

2009-2011

(After

Years)

Change

Including Loss

of

Quality of Life

SafetyBenefit ($)

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

Cost ($0.15 perfoot)

Benefit B-C Ratio

All Control

Sections86,835 1,699,417 19.57


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Putting together

Our Analysis 0.81

Safety Trend for theNarrow Rural 2-lane -5.6%

Final Estimated CMF 0.87


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HSM

CMF for Rural Two Lane

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


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Results Discussion

Implementing edge line is most likely to

reduce number of crashes based on our crash

analysis

The expected reduction is estimated 13%


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Summary

A very effective short-term

crash countermeasure for urban

undivided 4-lane roadway

Reducing crashes on rural freeway

Results in lower crash rate


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Thank You and Questions?

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