Desktop Reference 

 for 

 Crash Reduction Factors 

Report No. FHWA-SA-08-011 

U.S. Department of Transportation Federal Highway Administration S
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Notice 

This document is disseminated under the sponsorship of the U.S. Department othe interest of information exchange. The U.S. Government assumes no liabilitinformation contained in this document. This report does not constitute a standregulation. Quality Assurance Statement The Federal Highway Administration provides high-quality information to serv

industry, and the public in a manner that promotes public understanding. Standused to ensure and maximize the quality, objectivity, utility, and integrity of its 

periodically reviews quality issues and adjusts its programs and processes to enquality improvement. 
Technical Report Documentation Page 

1. Report No.: FHWA-SA-08-011 2. Government Accession No.: 3. Re4. Title and Subtitle 5. ReDesktop Reference for Crash Reduction Factors 6. Pe

iTRAN

7. Authors: Bahar, Geni; Masliah, Maurice; Wolff, Rhys; Park, Peter 8. Pe

Repo

9. Performing Organization Name and Address: 10. WiTRANS Consulting Ltd. Vanasse Hangen Brustlin, Inc 1220 L Street NW, #100-467 8300 Boone Blvd., Ste. 700 Washington, DC 2005-4018 Vienna, VA 22182-2626 (research) (editorial) 

11. CDTFH

13. TyCoveJanua

12. Sponsoring Agency Name and Address: U.S. Department of Transportation Federal Highway Administration (FHWA) Office of Safety 1200 New Jersey Avenue, SE Washington, DC 20590 14. S

FHWA

15. Supplementary Notes: FHWA Office of Safety Contract Task Order Manager Dr. Clayton Chen and Karen Y16. Abstract. This Desktop Reference documents the estimates of the crash reduction that might be expected i

or group of countermeasures is implemented with respect to intersections, roadway departure and other non-inpedestrian crashes. The estimates of crash reduction are known as Crash Reduction Factors (CRFs), and repravailable to date. Where available, the Desktop Reference includes multiple CRFs for the same countermeasureview the range of potential effectiveness. The CRFs are a useful as a guide, but it remains necessary to appl

to consider site-specific environmental, traffic volume, traffic mix, geometric, and operational conditions which wof a countermeasure. This report is a revision of Report FHWA-SA-07-015. 17. Key Words: crash reduction factor, CRF, intersection crashes, pedestrian crashes, roadway departure crashes 

18. Distribution Statement: No restrictions. This document is availthe National Technical Information Se

19. Security Classification (of this report): Unclassified 20. Security Classifications (of this 

page): Unclassified 

2P

Form DOT F 1700.7 (8-72) Reproduction of completed pages author
September 2008 

Table of Contents 

Forward ........................................................................................................................................................Introduction..................................................................................................................................................Tables for Intersection Crash Reduction Factors

Table 1: Signalization Countermeasures ...........................................................................................Table 2: Geometric Countermeasures................................................................................................Table 3: Signs / Markings / Operational Countermeasures ...............................................................

Tables for Roadway Departure Crash Reduction Factors

Table 4: Barrier Countermeasures .....................................................................................................Table 5: Bridge Countermeasures......................................................................................................Table 6: Geometric Countermeasures................................................................................................Table 7: Median Countermeasures ....................................................................................................Table 8: Roadside Countermeasures .................................................................................................Table 9: Signs / Markings / Operational Countermeasures ...............................................................

Tables for Pedestrian Crash Reduction Factors

Table 10: Signalization Countermeasures ........................................................................................Table 11: Geometric Countermeasures..............................................................................................Table 12: Signs / Markings / Operational Countermeasures .............................................................

References.....................................................................................................................................................
September 2008 

Desktop Reference for Crash Reduction Fa

Forward This report is a revision of Report FHWA-SA-07-015. This report includes hyperlinks to the source references, wh

References section in the electronic version of this report. 

Introduction This Desktop Reference provides estimates of the crash reduction that might be expected if a specific cou

countermeasures is implemented with respect to intersection crashes, roadway departure and other non-in

pedestrian crashes. The crash reduction estimates are known as Crash Reduction Factors (CRFs). The CR

information available to date. In some cases, the CRF is expressed as a Crash Reduction Function. Where available, the Desktop Reference includes multiple CRFs for the same countermeasure to allow thof potential effectiveness. This Desktop Reference includes CRFs for which the reliability of the estimate approach is part of the philosophy of bringing together all the information available to date. (A few CRFs not included in the Desktop Reference. These CRFs were considered to have too large a range or too large meaningful, or the original research did not provide sufficient detail for the CRF to be useful.) The CRFs 

may be periodically updated as new information becomes available. Crash Reduction Factors A CRF is the percentage crash reduction that might be expected after implementing a given countermeasuis negative, i.e. the implementation of a countermeasure is expected to lead to a percentage increase in craregarded as a generic estimate of the effectiveness of a countermeasure. The estimate is a useful guide, bapply engineering judgment and to consider site-specific environmental, traffic volume, traffic mix, geom

conditions which will affect the safety impact of a countermeasure. The user must ensure that a countermparticular conditions being considered. The reader is also encouraged to obtain and review the original so

detailed information, and to search databases such as the National Transportation Library (ntlsearch.bts.gbecomes available after the publication of this Reference. 
September 2008 

Traffic engineers and other transportation professionals can use the information contained in this issue brtypes of question: Which countermeasures might be considered at the signalized intersection of Maple anexperiencing a high number of total crashes and left-turn crashes? What change in the number of total cr

can be expected with the implementation of the various countermeasures? In the Tables presented in the Desktop Reference, CRFs are provided in the column “Crash Reduction Faerror of the CRF is given where available in the column “Std Error.” The standard error is the standard deestimate of the CRF. The true value of the CRF is unknown. The standard error provides a measure of the true value of the CRF. A relatively small standard error indicates that a CRF is relatively precisely knownerror indicates that a CRF is not precisely known. The standard error may be used to estimate a confidencthe CRF. (An example of a confidence interval calculation is given below.)

As an example, the CRF for the countermeasure install cameras to detect red-light running for right-angl

The following points should be noted:  The CRF of 16 means that a 16% reduction in fatal/injury crashes is expected after the installation of  This CRF is bolded which means that a) a rigorous study methodology was used to estimate the CRF, 

relatively small. A CRF which is not bolded indicates that a less rigorous methodology (e.g. a simple 

to estimate the CRF, and/or the standard error is large compared with the CRF. 

 The standard error for this CRF is 6. Using the standard error, it is possible to calculate the 95% confi

potential crash reduction that might be achieved by implementing the countermeasure. The 95% conferrors from the CRF. Therefore, the 95% confidence interval for the installation of red-light running c28% (16 - 2×6 = 4%, and 16 + 2×6 = 28%). 

 The reference number is 45 (Persaud et al., as listed in the References at the end of this Desktop Refe

Crash Reduction Functions In some cases, a CRF is given in the form of a function. As an example of a function, consider the countepresence” at 4-leg signalized intersections on rural highways. This function is shown in Table 3. The studBonneson et al. The function for “Vary truck presence” is: 
September 2008 

CRF = 100×[1-e(0.026×(Pt-9))] 

Where Pt = percent trucks during the peak hour (average for all intersection movements) The value of 9 in the function reflects the base condition: 9% trucks at 4-leg signalized intersections durinhighways (average for all intersection movements). If, for example, a practitioner wants to know the safetruck presence to 7%, then the resulting CRF value from the function would be 5 (=100×(1-e(0.026× (7-9)))). 

that crash frequency is reduced by about 5% for a 2 percentage point decrease in truck presence (from 9% 

Using the Tables Twelve Tables of CRFs are provided in this Reference. The Tables are grouped under intersection, roadw

crashes, and summarize the information available. The Tables include as much information as is available The Tables for intersection CRFs contain the following information (where available) for each countermeseverity, area type, configuration, control, major road daily traffic volume (vehicles/day), minor road dail(vehicles/day), reference, number of intersections observed, crash reduction factor/function, standard erro

The Tables for roadway departure CRFs contain the following information (where available) for each cou

crash severity, area type, road type, maximum daily traffic volume (vehicles/day), minimum daily traffic 

reference, crash reduction factor/function, standard error, range, and study type. The Tables for pedestrian CRFs contain the following information (where available) for each countermeaseverity, area type, reference, crash reduction factor/function, standard error, range, and study type. The following points should be noted:  The crash severities are: all, fatal/injury (fatal and injury crashes combined), fatal, injury, or property  Where available, the Tables provide existing traffic control information (i.e. the conditions existing b

countermeasure). The control information for the pre-countermeasure study site may be “no signal,” ““stop/yield.” “No signal” is used when a publication specifies that the intersection was not signalized 

was introduced, but does not provide details. (In these cases, the intersection could have yield or stop Where the original study is not clear, or omits to give the information, the cell is left blank. 


September 2008 

Road type information (for roadway departure countermeasures) uses the following road types (where 

multilane divided, arterial, highway, or freeway. Where the original study was not clear, or omitted to cell is left blank or the study’s wording is used. 

 In the observed column, a higher number of intersections/sites usually corresponds with a more reliab

effectiveness. 

 For some countermeasures, a range of safety effectiveness is provided in the Range Low and Range H The study type refers to the methodology used in the CRF study.  A blank cell means that no information is reported in the source document.  The following abbreviations appear in the Tables: 

o App = Approaches o Avg = Average o Config = Configuration o EB = Empirical Bayes o Emerg = Emergency o Max = Maximum o Min = Minimum o Obs = Number of observed intersections o PDO = Property Damage Only o Ped = Pedestrian o Ref = Reference o ROR = Run-Off-Road o Std Error = Standard Error 

 For additional information, please visit the FHWA Office of Safety website safety.fhwa.dot.gov. 
Tables for Intersection Crash Reduction Facto
Table 1: Signalization Countermeasures
Desktop Reference for Crash Reduction Factors 

Major Minor 

All All Signal 15 15 

Rightan

gle All Signal 15 30 

Add all-red clearance 

interval (from 0 to 1 second)

Rightangle All Urban Signal 47 6 0 

Add exclusive pedestrian phasing Ped All Signal 28 34 

All All Signal 25 -15 

Left-turn All Signal 25 -49 

All All Signal 62 1 

Left-turn All Signal 62 99 

All All Signal 62 0 

Left-turn All Signal 62 16 

All All Signal 25 -20 

All Fatal/Injury Signal 25 -10 

Left-turn All Signal 25 -65 

Rear-end All Signal 25 4 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

SIGNAL OPERATIONS COUNTERMEASURES

Obs 

Convert exclusive leading protected to exclusive lagging protectedConvert protected left-turn phase to protected/permissive

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Add all-red clearance 

intervalConvert permissive or permissive/protected to protected only leftturn phasingConvert permissive to permissive/protected left-turn phasing

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Signal 29 13 

Left-turn All Signal 29 33 

All All 4-Leg Signal 49

8

All All 4-Leg Signal 39 20 18All Fatal/Injury 4-Leg Signal 49 12 

Head-on Fatal/Injury Signal 15 75 

Left-turn All Signal 15 75Left-turn Fatal/Injury Signal 15 55 

Left-turn PDO Signal 15 63 

Multivehicle All All Signal 21 40 5 Multivehicle Fatal/Injury All Signal 21 40 9 

ROR Fatal/Injury Signal 15 62 ROR PDO Signal 15 28 

Olderdriver All 4-Leg Signal 39 20 42

Rear-end All 4-Leg Signal 49 -12 

Convert protected/permissive left-turn phase to permissive/protectedImprove signal timing [to intervals specified by the ITE Determining Vehicle Change Intervals: A Proposed Recommended Practice (1985)]

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Rear-end Fatal/Injury 4-Leg Signal 49 -8 

Rear-end PDO Signal 15 17 

Rightangle All 4-Leg Signal 49 4 Rightangle Fatal/Injury Signal 15 30 Rightangle Fatal/Injury 4-Leg Signal 49 -6 Rightangle PDO Signal 15 46 

Ped Fatal/Injury Signal 49 37

All All Signal 15 15 

Rightangle All Signal 15 30 

Install emergency vehicle pre-emption systems

Emerg 

vehicle All 51 70

All All Signal 15 20All All 15 25All All 15 15

Ped All Signal 15 53Ped All Signal 5 0Ped All 15 55Ped All 15 50

Increase yellow change intervalImprove signal timing [to intervals specified by the ITE Determining Vehicle Change Intervals: A Proposed Recommended Practice (1985)] (cont'd)Install pedestrian signal

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Modify signal phasing (implement a leading pedestrian interval)

Ped All Signal 28 5

Left-turn All Signal 15 80 

Rightangle All Signal 15 10 

Provide Advanced Dilemma Zone Detection for rural high speed approaches

All Fatal/Injury Rural 4-Leg (1 app) Signal 61 5 39 

All All Signal 15 30 

All All Signal 15 36 

All All Signal 15 15 

All All Signal 15 25 All All Signal 15 30 

All All Signal 15 27

Left-turn All Signal 15 41 Left-turn All Signal 15 46 Left-turn All Signal 15 35 Left-turn All Signal 15 70 Left-turn All Signal 15 48Left-turn Fatal/Injury Urban Signal 31 30 16

<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)

Provide actuated signalsProvide protected leftturn phase

>5,000/lane(Total)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Rightangle Fatal/Injury Urban Signal 31 30 19

Overturn All Signal 15 27 

Overturn All Signal 15 35 

Overturn All Signal 15 31

Ped All Signal 28 5

Rear-end All Signal 15 27 

Rear-end All Signal 15 35 

Rear-end All Signal 15 31

Rightangle All Signal 15 54 

Rightangle All Signal 15 56 Rightangle All Signal 15 80 Rightangle All Signal 15 63

Left-turn Fatal/Injury Urban Signal 31 15 16

Rightangle Fatal/Injury Urban Signal 31 15 12

Left-turn Fatal/Injury Urban Signal 31 20 17

Rightangle Fatal/Injury Urban Signal 31 20 25

All All All Signal 1 15All All Signal 28 16All All Arizona Signal 3 7

Rightangle All Signal 28 32 

<5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)>5,000/lane(Total)

Provide protected/permissive left-turn phase (leading flashing green) (Request MUTCD Ex

perimentation)

Provide protected leftturn phase (leading green arrow)Provide signal coordinationProvide protected leftturn phase (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Provide split phases All All Signal 28 25

All All Signal 28 29

Rightangle All Signal 47 17 75 

Rightangle All Signal 28 80

Replace existing WALK / DON'T WALK signals with pedestrian countdown signal heads

Ped All Urban (San Francisco) Signal 32 25

Add 3-inch yellow retroreflective sheeting to signal backplates

All All Urban Signal 54 15 

Olderdriver All 4-Leg Signal 39 33 31

Youngerdriver All 4-Leg Signal 39 33 17

All All Signal 28 10All All Urban 4-Leg Signal 14 63 28 

All Fatal/Injury Urban 4-Leg Signal 14 63 17 

All PDO Urban 4-Leg Signal 14 63 31 

Rear-end All Urban 4-Leg Signal 14 63 28 

Rightangle All Signal 28 42Rightangle All Urban 4-Leg Signal 14 63 35 

Add additional signal and upgrade to 12-inch lensesRemove flash mode (late night/early morning)SIGNAL HARDWARE COUNTERMEASURES

Add signal (additional 

primary head)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Signal 51 49All All Signal 35 6 25 

All All Signal 35 33 32 

All All Signal 28 36 All Fatal/Injury Signal 51 44All PDO Signal 51 51

Left-turn All Signal 51 12

Rear-end All Signal 51 41

Rightangle All Signal 51 74

Rightangle All Signal 35 6 63 

All All Urban Signal 52 224 7 

All Fatal/Injury Urban Signal 52 224 3 

All PDO Urban Signal 52 224 9 

Day All Urban Signal 52 224 6 

Night All Urban Signal 52 224 6 

All All Signal 28 9

Rightangle All Signal 28 36

All All All Signal 1 10All All Signal 28 11All All Signal 15 10All All Signal 15 10 All All Signal 28 11 All All Urban Signal 54 24 

Install larger signal lenses (12 inch)Convert signal from pedestal-mounted to mast armImprove visibility of signal heads (increase signal lens size, install new backboards, add reflective tape to existing backboards, and/or install additional signal heads)Improve visibility of signal heads (install two red displays in each head)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal/Injury Urban Signal 54 16 

Rightangle All Signal 47 44 46 Rightangle All Signal 28 48

All All Signal 28 13 

Rightangle All Signal 28 50 Rightangle All Signal 15 20Rightangle All Signal 15 20 

All All No signal 15 38 

All All No signal 15 20 

All All No si

gnal 28 33 

Left-turn All No signal 43 447 38 

Right-turn All No signal 43 447 50 

All All Rural No signal 43 447 15 

All Fatal No signal 43 447 38 

Rear-end All No signal 43 447 -48 

Rightangle All No signal 43 447 29 

All All Urban No signal 43 447 17 

All All No signal 15 22All All No signal 15 15 

All All No signal 15 13 

All All No signal 15 20 

>5,000/lane(Total)<5,000/lane(Total)

Install signal backplates (or visors)Install signalsInstall signal backplates onlyInstall larger signal lenses (12 inch) (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All No signal 15 25 All All No signal 15 20 

All Fatal/Injury Urban 3-Leg Stop 11,750- 42,000 900- 4,000 34 14 

All Fatal/Injury Urban 4-Leg Stop 12,650- 22,400 2,400- 3,625 34 23 

Overturn All No signal 15 22 

Overturn All No signal 15 20 

Rear-end All No signal 15 22 Rear-end All No signal 15 20 

Rear-end Fatal/Injury Urban 3-Leg Stop 11,750- 42,000 900- 4,000 34 -50 

Rear-end Fatal/Injury Urban 4-Leg Stop 12,650- 22,400 2,400- 3,625 34 -38 

Rightangle All No signal 15 74 

Rightangle All No signal 15 43 Rightangle All No signal 15 58

Rightangle All No signal 15 60 

Rightangle All No signal 15 42 Rightangle All No signal 15 65 

Rightangle All No signal 15 65 

Rightangle All No signal 28 68Rightangle All No signal 47 8 74 

Rightangle Fatal/Injury Urban 3-Leg Stop 11,750- 42,000 900- 4,000 34 34 

>5,000/lane(Total)<5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)

Install signals (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Rightangle Fatal/Injury Urban 4-Leg Stop 12,650- 22,400 2,400- 3,625 34 67 

All PDO No signal 43 447 -15 

Head-on PDO No signal 15 83 

Left-turn PDO No signal 15 11 

Rightangle Fatal/Injury No signal 15 39 Rightangle PDO No signal 15 73 

Sideswipe Fatal/Injury No signal 15 50 

Install signals (to have one over each approach lane)

Rightangle All All 35 46 

All All Signal 15 75All All Signal 15 100 

All All Signal 15 50 All All Signal 15 75 

All All Signal 28 52 All All Urban Signal 21 199 24 

All Fatal/Injury Urban Signal 21 199 53 

All PDO Urban Signal 21 199 24 

Day All Urban Signal 21 199 22 

Fixedobject All Urban Signal 21 199 31 

Night All Urban Signal 21 199 30 

Rear-end All Signal 15 95 

Install signals (temporary)Install signals (cont'd)Remove unwarranted signals

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Rear-end All Signal 15 100 

Rear-end All Signal 15 90 Rear-end All Urban Signal 21 199 29 

Rightangle All Urban Signal 21 199 24 

All All Signal 28 17 All All Signal 15 15All All Signal 15 15 

Head-on All Signal 15 20 

Left-turn All Signal 15 10 

Rear-end All Signal 15 10 

Rightangle All Signal 15 10 

Install left-turn lane and add turn phase All All Signal 28 58 

Head-on PDO No signal 15 27 

Left-turn PDO No signal 15 24 

ROR Fatal/Injury No signal 15 35 

Rightangle Fatal/Injury No signal 15 67 Rightangle PDO No signal 15 63 

Sideswipe Fatal/Injury No signal 15 54 

Install signals and add channelizationReplace signal lenses with optical lenses

COMBINATION SIGNAL AND OTHER COUNTERMEASURES

Remove unwarranted signals (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Stop >34,000 59 18 All All Stop >34,000 4 lanes 59 -24 All All Stop >34,000 6 lanes 59 26 All All Stop >34,000 8 lanes 59 24 All Fatal/Injury Stop >34,000 59 27 All PDO Stop >34,000 59 6 

Create directional median openings to allow left-turns and u-turns

All All Signal 51 51All All All 1 25All All Rural 3-Leg Signal 4,200- 26,000 1,300- 11,400 22 199 15 All All Rural 3-Leg Stop 1,100- 32,400 25- 11,800 22 44All All Rural 4-Leg (1 app) Signal 4,200- 26,000 1,300- 11,400 22 199 18 

All All Rural 4-Leg (1 app) Stop 1,100- 32,400 25- 11,800 22 28

All All Rural 4-Leg (2 app) Stop 1,100- 32,400 25- 11,800 22 48All All No signal 15 34All All No signal 15 35 

All All No signal 15 35 All All No signal 15 25 

All All No signal 15 40 

Add indirect left-turn treatments to minimize conflicts

LEFT-TURN COUNTERMEASURES

Install left-turn lane 

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All No signal 28 33 All All Urban 3-Leg Signal 4,600- 55,100 100- 26,000 22 199 7 All All Urban 3-Leg Stop 1,520- 40,600 80-8,000 22 33 All All Urban 4-Leg (1 app) Signal 4,600- 55,100 100- 26,000 22 10 

All All Urban 4-Leg (1 app) Stop 1,520- 40,600 80-8,000 22 27All All Urban 4-Leg (2 app) Signal 4,600- 55,100 100- 26,000 22 19 

All All Urban 4-Leg (2 app) Stop 1,520- 40,600 80-8,000 22 47All Fatal/Injury Rural 3-Leg Stop 1,100- 32,400 25- 11,800 22 55All Fatal/Injury Rural 4-Leg (1 app) Stop 1,100- 32,400 25- 11,800 22 35All Fatal/Injury Rural 4-Leg (2 app) Stop 1,100- 32,400 25- 11,800 22 58All Fatal/Injury Urban 4-Leg (1 app) Signal 4,600- 55,100 100- 26,000 22

9 

All Fatal/Injury Urban 4-Leg (1 app) Stop 1,520- 40,600 80-8,000 22 29All Fatal/Injury Urban 4-Leg (2 app) Signal 4,600- 55,100 100- 26,000 22 17All Fatal/Injury Urban 4-Leg (2 app) Stop 1,520- 40,600 80-8,000 22 50 

All Fatal/Injury All All All 58 30

Left-turn All Rural 3-Leg Stop 1,100- 32,400 25- 11,800 21 35 62 

Left-turn All Rural 4-Leg (1 app) Stop 1,100- 32,400 25- 11,800 21 23 37 Left-turn All Rural 4-Leg (2 app) Stop 1,100- 32,400 25- 11,800 21 23 60 Left-turn All No signal 15 55Left-turn All No signal 15 55 

Install left-turn lane (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Left-turn All No signal 28 68 Left-turn All Signal 15 24 

Left-turn All Urban 4-Leg (1 app) Signal 4,600- 55,100 100- 26,000 21 35 13 

Left-turn All Urban 4-Leg (1 app) Stop 1,520- 40,600 80-8,000 21 7 26 

Left-turn All Urban 4-Leg (2 app) Signal 4,600- 55,100 100- 26,000 21 35 24 

Left-turn All Urban 4-Leg (2 app) Stop 1,520- 40,600 80-8,000 21 7 45 

Night All Signal 15 28 

Overturn All Signal 15 28 

Head-on Fatal/Injury 15 75 

Left-turn Fatal/Injury 15 47 

Left-turn PDO 15 71 

ROR Fatal/Injury 15 8 ROR PDO 15 13 

Rear-end Fatal/Injury 15 29 

Rear-end PDO 15 32 

Rightangle Fatal/Injury 15 20 Rightangle PDO 15 8 

Sideswipe Fatal/Injury 15 50 

>5,000/lane(Total)>5,000/lane(Total)>5,000/lane(Total)

Install left-turn lane (cont'd)Install left-turn lane (double)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All 15 50 

All Fatal/Injury Rural 3-Leg 5,000- 15,000 13 22 All Fatal/Injury Rural 4-Leg 5,000- 15,000 13 -28 All PDO Rural 3-Leg 5,000- 15,000 13 20 All PDO Rural 4-Leg 5,000- 15,000 13 26 

Left-turn All 15 57 

Left-turn All 15 35 

Overturn All 15 54 

Overturn All 15 39 

Rear-end All 15 54 

Rear-end All 15 39 

Rightangle All 15 62 Rightangle All 15 49 

All All All No signal 1 35All All All Signal 1 25All All Rural 3-Leg No signal 28 44All All Rural 4-Leg (1 app) No signal 28 28All All 4-Leg (2 app) No signal 28 42All All 15 51 

All All 15 19 

All All Urban 3-Leg No signal 28 33

<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total) Install left-turn lane (painted separation)

Install left-turn lane (physical channelization)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Urban 4-Leg (1 app) No signal 28 27All Fatal/Injury Rural 3-Leg 5,000- 15,000 13 27 All Fatal/Injury Rural 4-Leg 5,000- 15,000 13 4 All PDO Rural 3-Leg 5,000- 15,000 13 -20 All PDO Rural 4-Leg 5,000- 15,000 13 16 

Left-turn All 15 24 

Left-turn All 15 24 

Left-turn Fatal/Injury 15 50 

ROR PDO 15 50 

Overturn All 15 50 

Overturn All 15 28 

Rear-end All 15 50 

Rear-end All 15 28 

Rear-end Fatal/Injury 15 11 

Rear-end PDO 15 56 

Rightangle All 15 68 Rightangle All 15 55 Rightangle Fatal/Injury 15 58 Rightangle PDO 15 54 

<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)

Install left-turn lane (physical channelization) (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Signal 28 31 All All Signal 51 35

Left-turn All Signal 28 44 

Olderdriver 

head-on

All 4-Leg Signal 39 13 73

Youngerdriver 

head-on

All 4-Leg Signal 39 13 66

All All Signal 28 23 

Left-turn All Signal 28 50 

All All Signal 15 35All All Signal 15 35 

All All Signal 15 35 All All 15 15All All 15 15 

All All 15 15 All All Signal 28 26

Left-turn All Signal 28 66

All All 15 24 

All All 15 44 

Head-on All 15 52 

Left-turn All 15 77 

Overturn All 15 44 

Install left-turn refuge within flush medianInstall left-turn lane (signal has left-turn phase)

<5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)>5,000/lane(Total)>5,000/lane(Total)

Install left-turn lane (signal has no turn phase)Install left-turn lane (with channelization and existing left-turn phase)Install left-turn lane (within existing curbs)Install left-turn lane (with channelization and no left-turn phase)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Overturn All 15 40 

Rear-end All 15 44 

Rear-end All 15 40 

Sideswipe All 15 52 

All All Rural 3-Leg Signal 6 -18All All Rural 4-Leg (1 app) Signal 6 -22All All Rural 4-Leg (2 app) Signal 6 -49All All Urban 3-Leg Signal 6 -8All All Urban 3-Leg Stop 6 -49All All Urban 4-Leg (1 app) Signal 6 -11All All Urban 4-Leg (1 app) Stop 6 -37All All Urban 4-Leg (2 app) Signal 6 -23All All Urban 4-Leg (2 app) Stop 6 -88All Fatal/Injury Rural 3-Leg Signal 6 -16All Fatal/Injury Rural 4-Leg (1 app) Signal 6 -21All Fatal/Injury Rural 4-Leg (2 app) Signal 6 -45All Fatal/Injury Urban 3-Leg Signal 6 -6All Fatal/Injury Urban 3-Leg Stop 6 -53All Fatal/Injury Urban 4-Leg (1 app) Signal 6 -10All Fatal/Injury Urban 4-Leg (1 app) Stop 6 -41All Fatal/Injury Urban 4-Leg (2 app) Signal 6 -21All Fatal/Injury Urban 4-Leg (2 app) Stop 6 -98

Install left-turn refuge within flush median (cont'd)

>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)>5,000/lane(Total)

Remove left-turn lane

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Increase length of right-turn lane All Fatal/Injury All All All 58 15

All All All 4-Leg (1 app) Signal 4,200- 55,100 100- 26,000 22

4

All All All 4-Leg (1 app) Stop 1,100- 40,600 25- 11,800 22 14All All All 4-Leg (2 app) Signal 4,200- 55,100 100- 26,000 22

8

All All All 4-Leg (2 app) Stop 1,100- 40,600 25- 11,800 22 26All All All All All 58 35All All All 1 25All All Rural 4-Leg (1 app) No signal 28 14All All Rural 4-Leg (1 app) No signal 28 21 All All All No signal 28 27 All All 15 25All All 15 25 All All 15 25 

All All 15 25 

All Fatal/Injury All 4-Leg (1 app) Signal 4,200- 55,100 100- 26,000 22

9

All Fatal/Injury All 4-Leg (1 app) Stop 1,100- 40,600 25- 11,800 22 23All Fatal/Injury All All No signal 58 35

All Fatal/Injury All All Signal 58 35All Fatal/Injury All All 51 40All Fatal/Injury Rural All All 58 35All Fatal/Injury Urban All All 58 30

Rear-end All 15 65 

RIGHT-TURN COUNTERMEASURES

Install right-turn lane

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Rightangle All 15 50 

Right-turn All 15 53Right-turn All 15 56 Right-turn All 15 50 

Sideswipe All 15 20 

Install right-turn lane (painted separation) All Fatal/Injury All All All 58 30Install right-turn lane (physical channelization)

All Fatal/Injury All All All 58 35

Install right-turn lane (cont'd)

FHWA-SA-08-011 September 2008 
Table 2: Geometric Countermeasures
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All 4-Leg No signal 28 57All Fatal/Injury Urban 4-Leg <70% >30% 13 33 

All Fatal/Injury Urban 4-Leg >85% <15% 13 -35 All Fatal/Injury Urban 4-Leg 70-85% 15-30% 13 25 

All PDO Urban 4-Leg <70% >30% 13 10 

All PDO Urban 4-Leg >85% <15% 13 -15 All PDO Urban 4-Leg 70-85% 15-30% 13 0 All All 4-Leg 51 57 All All All All 50 55 35

All All All Signal 50 9 48

All All All Signal 21 23 40 

All All All Stop (2-way) 50 36 44All All All Stop (4-way) 50 10 -3 

All All Rural 1-lane Stop (2-way) 50 9 72All All Rural Stop 7,185- 17,220 44 58All All 3-Leg 15 50 

All All 4-Leg 15 75 

OTHER GEOMETRIC COUNTERMEASURES

Convert four-leg to two T-intersections* Percentage of Total Daily Traffic VolumeConvert intersection to roundabout

**

*

**

* *

**

*

**

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal/Injury 55 181 65 

All PDO 55 181 42 

Ped All 55 181 89 

All All Urban Stop 13,272- 30,418 44 5 

All All Urban Signal 5,322- 31,525 44 35All All Urban Signal 50 5 1 

All All Urban Signal 21 4 35 

All All Urban Stop (2-way) 50 27 31All All Urban 1-lane Stop (2-way) 50 16 56All All Urban 2-lane Signal 50 4 67

All All Urban 2-lane Stop (2-way) 50 11 18All All Urban Stop 4,600- 17,825 44 72All Fatal/Injury All All 50 55 76

All Fatal/Injury All Signal 50 9 78

All Fatal/Injury All Stop (2-way) 50 36 82All Fatal/Injury All Stop (4-way) 50 10 -28 

All Fatal/Injury All All 21 23 80 

All Fatal/Injury Rural 1-lane Stop (2-way) 50 9 87

All Fatal/Injury Rural Stop 7,185- 17,220 44 82

Convert intersection to roundabout (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal/Injury No signal 11 62 44 

All Fatal/Injury Signal 11 34 32 

All Fatal/Injury 11 96 39 

All Fatal/Injury Urban Signal 50 5 60 

All Fatal/Injury Urban Stop (2-way) 50 27 74All Fatal/Injury Urban 1-lane Stop (2-way) 50 16 78All Fatal/Injury Urban 2-lane Stop (2-way) 50 11 72All Fatal/Injury Urban Signal 5,322- 31,525 44 74 All Fatal/Injury Urban Stop 4,600- 17,825 44 88

Ped Fatal/Injury No signal 11 27Ped Fatal/Injury Signal 11 -28

All All Rural 3-Leg Stop 6All All Rural 4-Leg Stop 6

Improve sight distance in 1 quadrant

All All Rural 4-Leg Stop/Yield (2-way) 23 5 

Improve sight distance in 2 quadrants

All All Rural 4-Leg Stop/Yield (2-way) 23 9

Improve sight distance in 3 quadrants

All All Rural 4-Leg Stop/Yield (2-way) 23 13All All Rural 4-Leg Signal 23 0All All Rural 4-Leg Stop/Yield (2-way) 23 17

Improve sight distance in 4 quadrantsConvert intersection to roundabout (cont'd)

100(1-EXP(0.0054angle - 90o|)); angl100(1-EXP(0.0048angle - 90o|)); angl

Improve intersection alignment (reduce skew)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal 51 56All Injury 51 37

Multiplevehicle All Rural 4-Leg Stop 24

4 

Multiplevehicle All Urban 3-Leg Stop 24 -3 

Multiplevehicle All Urban 4-Leg Signal 24 -3 

Multiplevehicle All Urban 4-Leg Stop 24 -6 

Multiplevehicle Fatal/Injury Rural 4-Leg Stop 24

4 

Multiplevehicle Fatal/Injury Urban 4-Leg Signal 24 -3 

Multiplevehicle Fatal/Injury Urban 4-Leg Stop 24 -5 

Increase pedestrian storage area at corner

All Fatal/Injury 5 -12 

Install median All All Rural Stop 6 27Install median islands (painted) on major road approaches

All Fatal/Injury All All All 58 15

Install median islands (physical) on major road approaches

All Fatal/Injury All All All 58 25All All No signal 28 25All All 28 25

Ped All No signal 28 69

Install raised median (marked crosswalk) Ped All 60 46Improve sight distance to intersectionIncrease median width by 3 ftInstall raised median

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Install raised median (unmarked crosswalk)

Ped All 60 39

Install refuge islands Ped All 28 56

All Fatal/Injury All 3-Leg All 58 45All Fatal/Injury All 4-Leg All 58 40All Fatal/Injury All All All 58 40All Fatal/Injury Rural All All 58 35All Fatal/Injury Urban All All 58 40All All Rural Stop 48 5 

Head-on PDO 3-Leg 15 13 

Left-turn Injury 3-Leg 15 36 Left-turn PDO 3-Leg 15 28 

ROR PDO 3-Leg 15 40 

Rear-end Injury 3-Leg 15 18 Rear-end PDO 3-Leg 15 21 

Rightangle Injury 3-Leg 15 24 Rightangle PDO 3-Leg 15 53 

Sideswipe PDO 3-Leg 15 30 

All All Rural Stop 6All All Urban 3-Leg Stop 6

Install splitter islands on minor road approachesVary median width

100(1-EXP(-0.012Wm=median width 100(1-EXP(0.0082Wm>161.0 for Wm<=16; W(ft)

Install turn and bypass lanes

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Urban 4-Leg Stop 6All Fatal/Injury Urban 3-Leg Stop 6All Fatal/Injury Urban 4-Leg Stop 6All All Rural

3-Leg 

and 4-

Leg

Stop 6

All All Urban Stop 6

Vary shoulder width

100(1-EXP(0.0173Wm>161.0 for Wm<=16; W(ft)100(1-EXP(0.0076Wm>161.0 for Wm<=16; W(ft)

Vary median width (cont'd)

100(1-EXP(0.016(Wm>161.0 for Wm<=16; W(ft)100(1-EXP(-0.02(WWs=outside should100(1-EXP(-0.03(WWs=outside should

FHWA-SA-08-011 September 2008 
Table 3: Signs / Markings / Operational Counterme
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All No signal 28 11

Rightangle All No signal 47 10 55 Rightangle All No signal 28 36

All All 3-Leg 15 70 

All All 4-Leg 15 39 

All All Signal 28 27 All All 15 25All All 15 25 All All 15 27 

All All 15 25 

Left-turn Fatal/Injury 15 67 

Left-turn PDO 15 79 

Rear-end All 4-Leg Signal 39 36

Rightangle All 4-Leg Signal 39 62Rightangle Fatal/Injury 15 73 

Rightangle Fatal/Injury 15 73 Rightangle PDO 15 62 

Install larger stop signs All All Stop 15 19 

All All 15 4

Ped All 15 15

>5,000/lane(Total)

SIGNS

Install double stop signsInstall flashing beacons as advance warningInstall pedestrian signing

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All All 1 35All All Signal 28 22 All All Urban 15 30 All All Rural 15 40

Rightangle All Signal 47 11 35 Rightangle All Signal 28 35

Rear-end All 51 10

Sidewipe All 51 20

All All No signal 28 29

Rightangle All No signal 28 24

All All No signal 28 9

Rightangle All No signal 28 0Rightangle All No signal 47 67 

Rightangle All No signal 28 67

All All 28 25

Wet All 28 59 

All All 15 25

Ped All 15 25Ped All 15 25Ped All 15 25Ped Fatal/Injury Rural 38 60 

All All 5 30 All Fatal/Injury 5 36 

Ped All 28 8

Install advance warning signs (positive guidance)Add centerline and move STOP bar to extended curb linesImprove/install pedestrian crossingInstall pedestrian crossingInstall pedestrian crossing (raised)Provide overhead lane-use signsAdd centerline and STOP bar, replace 24-inch with 30-inch stop signs

PAVEMENT MARKINGS/MODIFICATIONS

Add centerline and move STOP bar to extended curb lines, double stop signsImprove pavement friction (groove)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal/Injury 4-Leg 13 -5 All PDO 4-Leg 13 -13 All All 28 10 

Wet All 28 25 

Wet/Night All 28 33 

Install STOP bars (pedestrian crosswalk)

All All Signal 28 18 All All 28 19 

Rightangle All 28 47

All All 15 18 

Speedrelated Fatal/Injury Stop 18 57 

Speedrelated Serious injury Stop 18 74 

Speedrelated Slight injury Stop 18 52 

Speedrelated 

and day

All Stop 18 66 

Speedrelated 

and dry

All Stop 18 45 

Speedrelated All Stop 18 48 

Speedrelated 

and wet

All Stop 18 68 

Install raised pavement markersInstall transverse pavement markingsInstall raised intersectionInstall STOP bars (STOP bar on minor road approaches, with short segments of centerline)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Rural No signal 28 35All All Stop 15 28 

All All 28 23 

Rear-end All 15 90 

All All No signal 28 6

Rightangle All No signal 28 30Rightangle All Urban Stop 47 5 30 

Provide bicycle box (advance stop bar to leave dedicated space for cyclists)

Bicycle All Signal 51 35

Provide bike lanes Bicycle All 51 36

All All 28 33 

Wet All 28 47 

All All All Stop 21 141 -137

All All Urban 4-Leg Stop 33 -127 All All All Stop 21 360 47

All All No signal 28 64 All All Stop 15 53All Fatal/Injury Urban Stop 30 71 

Left-turn All Urban Stop 30 20 

Convert to all-way STOP control (from 2-

way control)

REGULATORY

Convert STOP control to Yield controlInstall transverse rumble strips on approachesResurface pavementMark pavement with supplementary warning messages

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Left-turn All Stop 15 20 

Ped All 15 39Ped All Urban Stop 30 39 

Rear-end All Urban Stop 30 13 

Rear-end All Stop 15 13 

Rightangle All Urban Stop 30 72 

Rightangle All No signal 28 84Rightangle All Stop 15 72 Rightangle All Urban Stop 47 10 80 

All All 15 26All All 15 26 

Convert to all-way STOP control (from 2-

way control) (cont'd)Convert two-way to one-way roadway

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All No signal 28 29

Rightangle All No signal 28 9

All All Urban 7 62 

Left-turn 

(or u-turn) All Urban 7 59 

All All Signal 5 -7 

All All Signal 10 -5 

Ped All New Orleans Signal 5 -81 

Ped All New York Signal 5 -43 Ped All Ohio Signal 5 -57 Ped All Wisconsin Signal 5 -108 

Right-turn Fatal/Injury Signal 13 -60 Right-turn PDO Signal 13 -10 

All All 15 45All All 15 45 

Left-turn All 15 90 

Ped All 15 10

Rear-end All 15 30 

All All Signal 28 23 

ROR All Signal 15 30 

Rear-end All Signal 15 20 

19,435-

42,000(Total)

19,435-

42,000(Total)

Prohibit right-turn-onredProhibit left-turnsInstall no left-turn and no u-turn signsConvert Yield control to STOP controlPermit right-turn-onred

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Urban/ Suburban Signal 62 

Rightangle All Signal 15 30 

Sideswipe All Signal 15 20 

Prohibit turns All turns All All 1 45 

All All 28 49 

Ped All 15 30

All All Rural 6All All Urban 6

Ped Fatal 5 78 Ped Injury 5 42 

All All Signal 51 30All Fatal/Injury Signal 51 17

Night All Signal 51 50

All All No Signal 28 47All All 62 4

All Injury 62 6

Night All 62 21

Night Injury 62 29

Restrict parking near intersections (to offstreet)

100(1-EXP(0.005(road speed limit (o(mph)100(1-EXP(0.019(road speed limit (o(mph)

LIGHTING

Vary speedInstall lightingImprove lighting at intersection

100(1-(0.984)^n); nsignalized intersecwhere RTOR is pro

Prohibit right-turn-onred (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Stop 15 28 All Injury Stop 15 43 

Rightangle All Stop 15 74 

All All Stop 15 36 All Injury Stop 15 53 

Rear-end All Stop 15 8 

Rightangle All Stop 15 74 

Increase enforcement related to motorist yielding in marked crosswalks combined with a public education campaign

Ped All 63 23

Increase enforcement to reduce speed

Ped All 28 70

Install angled median crosswalk All All 28 12

All All All 1 30 All All All 1 30All All Signal 28 34 All All 15 30All All 15 30 All All 15 4 

All All 15 30 

Install beacon (flashing) at intersectionConvert STOP control (2-way) to signal control and install left-turn lane

OPERATIONAL

Convert STOP control (2-way) to signal control

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All All Signal 17,000- 78,000 37 46 -12

All All Urban (Scottsdale) Signal 56 11 All Fatal/Injury All All Signal 58 5All Fatal/Injury Signal 17,000- 78,000 37 46 -14 

Left-turn All Urban (Scottsdale) Signal 56 14 45

Rear-end All Signal 52,625- 109,067 12,562- 33,679 45 -15Rear-end All Signal 17,000- 78,000 37 13 -57 Rear-end All Urban (Scottsdale) Signal 56 -41 Rear-end Fatal/Injury Signal 52,625- 109,067 12,562- 33,679 45 -24 

Rightan

gle All Signal 52,625- 109,067 12,562- 33,679 45 25

Rightan

gle All Urban (Scottsdale) Signal 56 14 20 

Rightan

gle Fatal/Injury Signal 52,625- 109,067 12,562- 33,679 45 16

Install far-side bus sto

ps

Ped All 28 1

All All No signal 15 25 

All All No signal 15 26 

All All No signal 15 26All Fatal/Injury No signal 15 50 

Head-on All No signal 15 50 

Rightan

gle All No signal 15 35 

Rightan

gle All No signal 15 36 

Rightan

gle All No signal 15 36

<5,000/lane(Total)>5,000/lane(Total)<5,000/lane(Total)>5,000/lane(Total)

Install flashing red/yellow signal (MUTCD: intersection control beacon)Install cameras to detect red-light running

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

Install pedestrian crossing (signed and marked with curb ramps and extensions)

All All No signal 28 37 

Install pedestrian overpass/underpass Ped All No signal 28 13

All All Urban Stop 53 50 All Fatal/Injury Urban Stop 53 67 All All Rural Signal 6All All Rural Stop 6All All Urban Signal 6All All Urban Stop 6

Vary sight distance All All Rural Signal 6 0

All All Rural Signal 6All All Rural Stop 6All All Rural 4-Leg Signal 6All Fatal/Injury Rural 3-Leg Stop 6

100(1-EXP(-0.093Nln=number of thrroad100(1-EXP(0.026(truck during the pefor all intersection 100(1-EXP(-0.025Pt=percent truck dhour (average for amovements)100(1-EXP(0.046(Nd=number of drivmajor road within 2intersection100(1-EXP(0.056(Nd=number of drivmajor road within 2intersection100(1-EXP(0.007(Nln=number of thrroad100(1-EXP(-0.057width (ft)100(1-EXP(-0.053width (ft)

Vary through lanesVary lane widthVary frequency of driveways within 250 ft of intersectionVary truck presenceInstall stop signs at alternate intersections in residential areas

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Major Minor 

Ref

Effecti

Crash Reduction 

Factor / Function

Daily Traffic 

Volume (veh/day)

Obs 

Area Type Control Crash Severity Crash Type Countermeasure(s) Config

All Fatal/Injury Rural 4-Leg Stop 6All Fatal/Injury Rural 4-Leg Signal 6

100(1-EXP(-0.052Pt=percent truck dhour (average for amovements)100(1-EXP(0.0323Pt=percent truck dhour (average for amovements)

Vary truck presence (cont'd)

FHWA-SA-08-011 September 2008 
Tables for Roadway Departure Crash Reduction F
Table 4: Barrier Countermeasures
Desktop Reference for Crash Reduction Factors Roa

All All <5,000/lane 15 18All All >5,000/lane 15 9All All All All 1 5All All 15 5All All 15 6All All 15 7All All 15 7All All 15 11All All 15 15All All 15 15All All 15 20All Fatal All All 1 50All Injury 15 35All Injury All All 1 35

Fixed 

object All <5,000/lane 15 23

Fixed 

object All >5,000/lane 15 18

Fixed 

object All 15 21

ROR All 15 26ROR All >5,000/lane 15 32ROR All 15 28

Overturn All <5,000/lane 15 41Overturn All >5,000/lane 15 27Overturn All 15 34

Rear-end All <5,000/lane 15 41Rear-end All >5,000/lane 15 27Rear-end All 15 34

Animal All 15 80Animal All All All 1 90Animal All 15 70Animal All 15 90Animal Injury 15 91

Install animal fencing

Daily Traffic 

Volume 

(veh/day)

Road Type 

Improve guardrail

BARRIER COUNTERMEASURES

Crash 

Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Animal PDO 15 61Animal 

head-on All 15 85

All All 15 14All Injury 15 31

Fixed 

object All 15 100

All Fatal 15 65All Injury 15 51All All 15 27All All 15 24All All 15 30

Install guardrail (at ditch) All Injury 15 26

All Injury 15 42

ROR All All 5 7 31 ROR Fatal All 5 44 10 ROR Injury All 5 47 5 

All All 15 29All All All All 1 5All All 15 5All All 15 20All All 15 20All All 15 35All All 15 41

Install animal fencing (cont'd)Install impact attenuatorsInstall guardrail (as shield for rocks and posts)Install barrier (concrete) inside and outside curve

15 63 Fatal/ Injury15 3915 28

Fatal/ 

Injury All

All

Install guardrail (as shield for trees)Install guardrail (at culvert)Install guardrail (at embankment)Install guardrail (inside curves) All Fatal/ Injury

Install guardrail (outside curves)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 50All Fatal All All 1 75All Fatal 15 75All Fatal 15 83All Fatal 15 90All Injury All All 1 50All Injury 15 50

Fixed 

object Fatal All All 5 69 28 

Fixed 

object Injury All All 5 69 10 

Fixed 

object PDO 5 46 30 

ROR All 15 45ROR Fatal All 5 41 31 ROR Injury All 5 32 10 

Install impact attenuators (cont'd)Replace guardrail with a softer material (concrete

→steel

→wire)

FHWA-SA-08-011 September 2008 
Table 5: Bridge Countermeasures
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Install bridge lighting All All 15 59

All All 15 43All All 15 39All All 15 40All All 15 50All All <5,000/lane 15 22All All >5,000/lane 15 20All All 15 11All All 15 24All All 15 24All All 15 44All Fatal 15 90All Injury 15 45

Overturn All <5,000/lane 15 41Overturn All >5,000/lane 15 32

Rear-end All <5,000/lane 15 37Rear-end All >5,000/lane 15 32

Wet All 15 50

All All 15 14All All 15 13All All 15 15

Replace bridge (general) All All All All 1 45Replace bridge (2-lane) All All 15 45Upgrade bridge parapet All All 15 5

All All 15 20All All All All 1 5All Fatal 15 76All Fatal 15 60All Fatal 15 92

Install guardrail (at bridge)Repair bridge deckInstall delineators (on bridges)

BRIDGE COUNTERMEASURES

Upgrade bridge railing

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All Injury 15 61All Injury All All 1 30All Injury 15 30All Injury 15 92All PDO 15 50

Vary bridge width All All Rural Rural Highway

6

Vary horizontal bridge radius All All Urban Urban Street 6

All All 15 45All All All All 1 45All All 15 36All All 15 40All All 15 45All All 15 47All All 15 48All All 15 55All PDO 15 95

Fixed 

object All 15 45

Fixed 

object All 15 40

Fixed 

object All 15 50

Head-on All 15 45

Widen bridge All Fatal/ Injury 92

Upgrade bridge railing (cont'd)

15

100(1-(EXP(-0.135Ibr(Wb-12)Ibr=presence of bridges (1 if obridges present, 0 if not), Wb=approach traveled-way width (Ps=proportion of crash type svalues of Ps, refer to source).100(1-(2.30(EXP(-2298/R)+34road)+0.781(EXP(320.9/R)Poroad=proportion of crashes throadway.

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Head-on All 15 40Head-on All 15 50

ROR All 15 44

Sideswipe All 15 49Sideswipe All 15 40Sideswipe All 15 50Sideswipe All 15 57

Widen bridge (18 to 24 ft) All All 15 68Widen bridge (18 to 30 ft) All All 15 93Widen bridge (20 to 24 ft) All All 15 56Widen bridge (20 to 30 ft) All All 15 90Widen bridge (22 to 24 ft) All All 15 36Widen bridge (22 to 30 ft) All All 15 86Widen bridge (cont'd)

FHWA-SA-08-011 September 2008 
Table 6: Geometric Countermeasures
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Change shoulder type and/or width All All Rural 21 

All All All All 27 20 19 

All Fatal/ Injury All All 27 51 19 

All Fatal/ Injury Rural 2-lane 38 50

All All 15 39All All All All 1 40All All 15 35All All Rural 21 All Fatal 15 87All Injury 15 87All PDO 15 87

Fixed 

object All <5,000/lane 15 68

100(1-((AMFWRA x AMFTRA1.0)PRA+1.0)), AMFWRA=acmodification factor for related based on shoulder width (for vAMfWRA, refer to source), AMFTRA=accident modificatiorelated accidents based on sh(for values of AMFTRA, refer PRA=proportion of total crashby related crashes. 

GEOMETRIC COUNTERMEASURES

Flatten horizontal curveFlatten crest vertical curve

100(1-((1.55Lc+80.2/R-0.012ILc=length of horizontal curve spirial curve length, R=curve rIs=presence of a spiral transita spiral transition is present, 0 

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Fixed 

object All >5,000/lane 15 87

Head-on All <5,000/lane 15 67Head-on All >5,000/lane 15 64

ROR All <5,000/lane 15 90ROR All >5,000/lane 15 79

Overturn All <5,000/lane 15 73Overturn All >5,000/lane 15 24

Rear-end All <5,000/lane 15 73Rear-end All >5,000/lane 15 24Rear-end All 15 49

Flatten horizontal curves (10 to 5 degrees) All All 15 45Flatten horizontal curves (15 to 5 degrees) All All 15 63Flatten horizontal curves (20 to 10 degrees) All All 15 48

All All <5,000/lane 15 43All All >5,000/lane 15 45All All All All 1 30All All 15 25All All 15 30All All 15 32All All 15 35

Fixed 

object All 15 62

ROR All 15 10

All All 15 8

Ped All 15 14

Right-turn All 15 14

Flatten horizontal curve (cont'd)Flatten side slopesFlatten side slopes (11 to 8 degrees)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 7All Injury Rural 2-lane 5 22

4 

All PDO Rural 2-lane 5 24

2 

Ped All 15 12

Right-turn All 15 12

All All Rural 2-lane 15 11

ROR All Rural 2-lane 5 24 21 

Ped All Rural 2-lane 15 19

Right-turn All 15 19

All All 15 8

Ped All 15 14

Right-turn All 15 14

All All 15 5All Injury Rural 2-lane 5 42

4 

All PDO Rural 2-lane 5 29

4 

ROR All Rural 2-lane 5 18 16 

Ped All 15 8

Right-turn All 15 8

All All 15 12

Ped All 15 21

Right-turn All 15 21

All All 15 9

Ped All 15 15

Right-turn All 15 15

All All 15 6

Ped All 15 10

Right-turn All 15 10

Flatten side slopes (27 to 9 degrees)Flatten side slopes (27 to 14 degrees)Flatten side slopes (27 to 11 degrees)Flatten side slopes (18 to 14 degrees)Flatten side slopes (18 to 9 degrees)Flatten side slopes (18 to 11 degrees)Flatten side slopes (14 to 9 degrees)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Flatten side slopes and remove guardrail All All All All 27 42 58 

All All Rural All 21 0 All All Rural 21 All All Rural 21 All All 15 25All All All All 1 25All All 15 58All All All All 1 50All All 15 50All All 15 50All All 15 73All All 15 49All All All All 1 40All All 15 40All All 15 57All PDO 15 83All All 15 40All All 1 40

ROR All 15 50

All All 15 45All All 15 40All All 15 49All All <5,000/lane 15 20All All >5,000/lane 15 31All All 15 10All All 15 20All All 15 22

Increase number of lanesImprove superelevation (for drainage)Improve superelevationImprove curve superelevation 100(1-(1.06+3(SD-0.02))); 

SD=superelevation deficiency 0.02

All 15 87 Fatal/ Injury

Improve horizontal and vertical alignmentsImprove longitudinal gradeImprove gore area

100(1-(1.00+6(SD-0.01))); SD=superelevation deficiency and 0.02

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 25All All 15 25All All 15 25All Fatal 15 39All Injury 15 23All PDO 15 27

Head-on All <5,000/lane 15 38Head-on All >5,000/lane 15 44Head-on All 15 53Head-on All 15 53Head-on PDO 15 50

Left-turn All 15 71Left-turn PDO 15 67

ROR All 15 44ROR All 15 26ROR All 15 44ROR All 15 44ROR PDO 15 50

Overturn All <5,000/lane 15 42Overturn All >5,000/lane 15 52

Rear-end All <5,000/lane 15 42Rear-end All >5,000/lane 15 52Rear-end All 15 32Rear-end All 15 32Rear-end All 15 40Rear-end All 15 53Rear-end PDO 15 53

Rightangle All <5,000/lane 15 35Rightangle All >5,000/lane 15 45Rightangle All 15 15Rightangle PDO 15 46

Sideswipe All <5,000/lane 15 38

Increase number of lanes (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Sideswipe All >5,000/lane 15 44Sideswipe All 15 30Sideswipe All 15 30Sideswipe All 15 35Sideswipe PDO 15 64

Increase vertical grade by 1% All All Rural 2-lane 23

All All 15 26All All All All 1 10All All 15 10All All 15 10All All 15 10All All 15 25All All 15 75

Rear-end All 15 75

Sideswipe All 15 75

All All 15 67All PDO 15 62

Rear-end All 15 93

Install climbing lane (where large difference between car and truck speed)

All Fatal/ Injury Rural 2-lane 38 33

All All All All 1 20All Fatal/ Injury Rural 2-lane 38 33

Install shoulder All All 15 9

Head-on Fatal/ Injury 15 50

Head-on PDO 15 86

Left-turn Fatal/ Injury 15 42

Left-turn PDO 15 57

Install passing/climbing laneInstall shoulder bus lanes

-1.6P; P=percent grade (abso

Install acceleration/ deceleration lanesInstall channelized laneIncrease number of lanes (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

ROR PDO 15 27

Rightangle Fatal/ Injury 15 34Rightangle PDO 15 31

Sideswipe Fatal/ Injury 15 27

Sideswipe PDO 15 8

All All 15 18

ROR All 15 75

Rear-end All 15 33

All All 15 44All All 15 40All All 15 48All All 15 30All All Urban 4-lane highway 8,000-17,400 17 37 1 All All 4-lane 42 26 All Fatal/ Injury Urban 4-lane highway 8,000-17,400 17

0

2 

All PDO Urban 4-lane highway 8,000-17,400 17 46 1 

Left-turn All Urban 4-lane highway 8,000-17,400 17 24

2 

Rear-end All Urban 4-lane highway 8,000-17,400 17 31

2 

Rightangle All Urban 4-lane highway 8,000-17,400 17 37 1 

All All Urban 3,718-26,376 62 29

2 

All All 15 38All All 15 40

Reduce shoulder width (6 ft to 0 ft) All All Rural 2-lane 20 -12 3 Reduce horizontal curve angleInstall shoulder bus lanes (cont'd)Install truck escape rampLengthen culvertsNarrow cross section (4 to 3 lanes with two way left-turn lane)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Reduce shoulder width (6 ft to 1 ft) All All Rural 2-lane 20 -17 6 Reduce shoulder width (6 ft to 2 ft) All All Rural 2-lane 20 -11 2 Reduce shoulder width (6 ft to 4 ft) All All Rural 2-lane 20 -6 2 Reduce shoulder width (6 ft to 5 ft) All All Rural 2-lane 20 -2 2Reduce vertical grade by 1% All All Rural 2-lane 23 

All All 15 28

Wet 

pavement All 15 51

Stabilize shoulder All All 15 25Stabilize shoulder and dropoff All All All All 1 25

All All Freeway 6All All Rural Rural Highway

6

Vary horizontal curvature All All Rural Rural Highway

6

Vary gradeResurface pavement and improve superelevation

1.6P; P=percent grade (absol100(1-((1.55Lc+80.2/R-0.012ILc=length of horizontal curve radius (ft), Is=presence of a spcurve (1 if a spiral transition is otherwise).100(1-(EXP(bPg-1.0)1.0+1.0)b=regression coefficient (for vrefer to source)., Pg=percent g(absolute value).100(1-((EXP(bPg)-1.0)Ps+1.0b=regression coefficient (for vrefer to source), Pg=percent gvalue), Ps=proportion of crash (for values of Ps, refer to sour

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All Freeway 6All All Rural Rural Highway

6

All All Freeway 6All All Rural Rural Highway

6

All All Urban Urban Street 6

Vary outside shoulder width All All Freeway 6Vary inside shoulder width

100(1-((EXP(-0.021(Wis-Wsb1.0)(Pi/0.15)+1.0)); Wis=inside width (ft), Wsb=base inside sh(ft) (=4.0 for four lanes, 10.0 folanes), Pi=proportion of crash (for values of Pi, refer to sourc100(1-((EXP(-0.021(Wis-4))-1.0)(Pi/0.16)+1.0)); Wis=inside width (ft), Pi=proportion of cra(for values of Pi, refer to sourc

Vary lane width

100(1-((EXP(-0.047(Wl-12))-1.0)(Pi/0.36)+1.0)); Wl=lane wPi=proportion of crash type suvalues of Pi, refer to source).100(1-((EXP(-0.040(Wl-12))-1.0)(Pi/0.24)+1.0)); Wl=lane wPi=proportion of crash type suvalues of Pi, refer to source)100(1-((EXP(-0.021(Ws-10))-1.0)(Pi/0.15)+1.0)); Ws=outsidwidth (ft), Pi=proportion of cra(for values of Pi, refer to sourc100(1-((EXP(-0.047(Wl-12))-1.0)(Pi/0.37)+1.0)); Wl=lane wPi=proportion of crash type suvalues of Pi, refer to source).

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Vary outside shoulder width (cont'd) All All Rural Rural Highway

6

Vary shoulder width All All Urban Urban Street 6Vary side slopes All All Rural Rural Highway

6

Vary spiral transition curvature All All Rural Rural Highway

6

Vary superelevation All All Rural Rural Highway

6

Vary uncurbed crosssections All All Urban Urban Street 6

Head-on All 15 12

ROR All 15 12

Sideswipe All 15 12

Head-on All 15 23

ROR All 15 23

Widen lane (add 2 ft to both sides) (cont'd) Sideswipe All 15 23

100(1-((EXP(-0.074)(1-Poff-ro0.225)Poff-road)); Poff-road=poff-road crashes.100(1-((EXP(-0.021(Ws-8))-1.0)(Pi/0.16)+1.0)); Ws=outsidwidth (ft), Pi=proportion of cra(for values of Pi, refer to sourc100(1-((EXP(-0.014(Ws-1.5))-1.0)(Pi/0.088)+1.0)); Ws=shouPi=proportion of crash type suvalues of Pi, refer to source).

Widen lane (add 1 ft to both sides)Widen lane (add 2 ft to both sides)

100(1-((1.55Lc+80.2/R0.012)/(1.55Lc+80.2/R))); Lc=horizontal curve (mi), R=curve 0 through -15 according to the superelevation deficiency (refe100(1-((EXP(0.692(1/Ss-0.25)1.0)Ps+1.0)), Ss= horizontal rchange in elevation (average segment, ft), Ps=proportion of subset (for values of Ps, refer 

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Head-on All 15 32

ROR All 15 32

Sideswipe All 15 32

Head-on All 15 40

ROR All 15 40

Sideswipe All 15 40

Widen lane (initially less than 9 ft) All Fatal/ Injury Rural 2-lane 400-2,000 38 28 

Widen lane (initially between 9 ft and 10.75 ft)

All Fatal/ Injury Rural 2-lane 400-2,000 38 16 

All All All 15 56All All Rural 21 All All 15 50

Fixed 

object All 15 5

Head-on All 15 70Head-on All 15 5Head-on All 15 70

ROR All 15 49

Overturn All 15 5

Sideswipe All 15 52Sideswipe All 15 5Sideswipe All 15 52

Widen shoulder (from 6 to 7 ft) All All Rural 2-lane 20 -1 4

Widen lanesWiden lanes (cont'd)Widen lane (add 3 ft to both sides)Widen lane (add 4 ft to both sides)

100(1-((AMFRA-1.0)PRA+1.0AMFRA=accident modification related accidents (for values orefer to source), PRA=proportcrashes constituted by related 

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Widen shoulder (from 6 to 8 ft) All All Rural 2-lane 20 4 2

Widen shoulder (from 6 to 9 ft) All All Rural 2-lane 20 21 6Widen shoulder (from 6 to >9 ft) All All Rural 2-lane 20 18 3Widen shoulder All All All All 1 20Widen shoulder (initially less than 1 ft) All Fatal/ Injury Rural 2-lane 400-2,000 38 25 

Widen shoulder (initially between 1 ft and 3.3 ft) All Fatal/ Injury Rural 2-lane 400-2,000 38 13 

Widen shoulder (initially less than or equal to 4 ft) All All All All 1 20

Widen shoulder (initially more than 4 ft) All All All All 1 35

All All 15 29All All 15 57All All 15 20All All 15 8All All 15 32All All 15 50

Fixed 

object All 15 15

Head-on All 15 45Head-on All 15 75Head-on All 15 15

ROR All 15 60

Ped All 15 71

Sideswipe All 15 28Sideswipe All 15 41Sideswipe All 15 15

Widen shoulder (paved)Widen shoulder (paved) (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Fixed 

object All 15 16

ROR All 15 16

Fixed 

object All 15 29

ROR All 15 29

Fixed 

object All 15 40

ROR All 15 40

Fixed 

object All 15 49

ROR All 15 49

All All Rural 2-lane 15 15All All 15 22

Fixed 

object All 15 13

ROR All 15 13

Fixed 

object All 15 25

ROR All 15 25

Fixed 

object All 15 34

ROR All 15 34

Fixed 

object All 15 43

ROR All 15 43

Widen shoulder (unpaved) (from 0 to 8 ft)Widen shoulder (paved) (from 0 to 2 ft)Widen shoulder (unpaved)Widen shoulder (unpaved) (from 0 to 2 ft)Widen shoulder (unpaved) (from 0 to 4 ft)Widen shoulder (unpaved) (from 0 to 6 ft)Widen shoulder (paved) (from 0 to 6 ft)Widen shoulder (paved) (from 0 to 8 ft)Widen shoulder (paved) (from 0 to 4 ft)

FHWA-SA-08-011 September 2008 
Table 7: Median Countermeasures
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All All All 1 15All Fatal/ Injury Rural 2-lane 5 -94 56 

All Fatal/ Injury Urban 2-lane 5 39 10 All Injury Rural Multilane 5 12 3 

All Injury Urban Multilane 5 22 2 

All PDO Rural Multilane 5 18 3 

All PDO Rural 2-lane 5 -128 55 

All PDO Urban Multilane 5 -9 2 

All All <5,000/lane 15 44All All >5,000/lane 15 52All All All All 1 25All All 15 15All All 15 15All Fatal 15 90

Left-turn All <5,000/lane 15 72Left-turn All >5,000/lane 15 78

All All All All 27 86

3 

All All Multilane divided 5 -24 3 

All All 15 19All All All All 1 5All All 15 5All All 15 15All All 15 19All All 15 20All All 15 25All All 15 25

Install median barrier

MEDIAN COUNTERMEASURES

Install medianInstall median (flush)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 36All Fatal Multilane divided 5 43 10 

All Fatal All All 1 65All Fatal 15 65All Fatal/ Injury All All 27 88

5 

All Injury Multilane divided 5 30 6 

All Injury All All 1 40All Injury 15 40

ROR All 15 35

Rightangle All <5,000/lane 15 58Rightangle All >5,000/lane 15 54

All All Highway (three-lane) 5 -34 74 

All Fatal Highway (three-lane) 5 100 254 

All Injury Highway (three-lane) 5 26 84 

All Injury Multilane divided 5 29 11 

Head-on Fatal Rural Highway 9 92 

All Fatal 15 90All Injury Multilane divided 5 -15 36 

All Injury 15 10

Install median barrier (steel) All Injury Multilane divided 5 35 8 

Install median barrier (cont'd)Install median barrier (concrete)Install median barrier (cable)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All <5,000/lane 15 17All All >5,000/lane 15 17All All 15 17

ROR All <5,000/lane 15 56ROR All >5,000/lane 15 56ROR All 15 56

Rear-end All <5,000/lane 15 39Rear-end All >5,000/lane 15 39Rear-end All 15 39

All All 15 20All All 15 25

Head-on All 15 75

Ped All 15 25

All All Urban Urban Street 6All All Rural Rural Highway

6

All All Freeway 6

Install raised medianInstall or upgrade median barrier near gore area

100(1-((b0(EXP(b1Wm^b2)-1.0)+1.0)/(b0(EXP(b1Wmb^b2b0, b1, and b2=regression coevalues of b0, b1, and b2, refer Wm=median width (ft), Wmb=width (ft) (16 for surfaced meddepressed median).100(1-((b0(EXP(b1Wm^b2)-1.0)+1.0)/(b0(EXP(b1Wmb^b2b0, b1, and b2=regression coevalues of b0, b1, and b2, refer Wm=median width (ft), Wmb=width (ft) (24 for surfaced meddepressed median).

Vary median width

100(1-((b0(EXP(b1Wm^b2)-1.0)+1.0)/(b0(EXP(b1x16b^b2b0, b1, and b2=regression coevalues of b0, b1, and b2, refer Wm=median width (ft).

FHWA-SA-08-011 September 2008 
Table 8: Roadside Countermeasures
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 40All All All All 1 40

Snow All 15 53Snow All 15 71Snow All 15 35

Remove poles by burying utility lines All All 15 40Remove obstacles on curves to improve sight distance

All Fatal/ Injury Rural 2-lane 38 5

All All All All 27 38 10 

All All <5,000/lane 15 18All All >5,000/lane 15 17All All All All 1 30All All All All 1 25All All 15 29All All 15 35All All 15 61All All 15 20All All 15 25All All 15 30All All 15 30All All 15 55All All 15 25All Fatal All All 1 50All Fatal All All 1 40All Fatal 15 40All Fatal 15 50All Fatal 15 40All Fatal 15 50All Fatal/ Injury All All 27 38 13 

All Injury All All 1 30

ROADSIDE COUNTERMEASURES

Install snow fencingInstall frontage roadRemove or relocate fixed objects outside of clear zone

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All Injury All All 1 25All Injury 15 25All Injury 15 30All Injury 15 25All Injury 15 30

Fixed 

object All 15 65

Fixed 

object All Urban 15 20

Fixed 

object All <400 15 40

Fixed 

object All 15 88

Fixed 

object All 15 90

Fixed 

object All 15 100

Fixed 

object All 15 75

ROR All 15 71

Overturn All <5,000/lane 15 42Overturn All >5,000/lane 15 44

Vary horizontal clearance All All Rural Rural Highway

6

Vary utility pole density All All Freeway 6

100(1-((EXP(-0.0137(Whc-301.0)Ps+1.0)); Whc=horizontal (average for length of segmenPs=proportion of crash type svalues of Ps, refer to source).100(1-((fp-1.0)Ps+1.0)); fp=((0.0000984ADT+0.0354D0.04)/(0.0000128ADT+0.075)pole density (two-way total) (p=average pole offset from neatraveled way (ft), Ps=proportiotype subset (for values of Ps, source).

Remove or relocate fixed objects outside of clear zone (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All Rural Rural Highway

6

All All Urban Urban Street 6

Widen clear zone (add 5 ft)

Fixed 

object All 15 13

Widen clear zone (add 8 ft)

Fixed 

object All 15 21

Widen clear zone (add 10 ft)

Fixed 

object All 15 25

Widen clear zone (add 15 ft)

Fixed 

object All 15 35

Widen clear zone (add 20 ft)

Fixed 

object All 15 44

Vary utility pole density (cont'd)

100(1-((fp-1.0)Ps+1.0)); fp=((0.0000984ADT+0.0354D0.04)/(0.0000128ADT+0.075)pole density (two-way total) (p=average pole offset from neatraveled way (ft), Ps=proportiotype subset (for values of Ps, source)100(1-(0.022(fp-1.0)+1.0)), fp=((0.0000984ADT+0.0354D0.04)/(0.0000649ADT+1.128)pole density (two-way total) (pWo=average pole offset from of traveled way (ft) 

FHWA-SA-08-011 September 2008 
Table 9: Signs / Markings / Operational Counterme
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All Injury Urban Local 5 15 10 

All PDO Urban Local 5

7

6 

All Fatal/ Injury Rural 2-lane 38 20

All All 15 35All All Urban Arterial (urban) 5 64 49 

All All 15 20All All 15 35All All 15 50All Fatal/ Injury Rural 2-lane 38 10

All Injury 5 30 71 

All PDO 5 8 76 

All All 15 30All Fatal 15 55All All 15 30All All 15 23All Injury 15 20

Head-on All 15 29

ROR All 15 30ROR All All All 1 30

All Injury 5 13 9 

All PDO 5 29 23 

All All 15 29All All 15 20

SIGNS

Install curve advance warning signs (advisory speed)Install curve advance warning signsImplement sign corrections to MUTCD standardsInstall chevron signs on horizontal curves

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Install curve advance warning signs (flashing beacon)

All All 15 30All All 15 11

Head-on All 15 67

Night All 15 25

ROR All 15 34

Sideswipe All 15 67

All Injury Freeways 5 44 17 

Rear-end Injury Freeways 5 16 10 

Install dynamic/variable queue warning signs Rear-end PDO Freeways 5 -16 15 

All All 5 46 17 

All Injury 5 41 62 

Install guide signs (general) All All All 15 15Install guideposts or barrier reflectors All Fatal/ Injury Rural 2-lane 38 8

Install illuminated signs All All 15 15

Rear-end All 15 10

Sideswipe All 15 20

All All 15 10

Night All 15 25

All All 15 5

Wet 

pavement All 15 20

Wet 

pavement All 15 20

Wet 

weather All All All 1 20

Install dynamic/variable speed warning signsInstall delineators (general)Install pavement condition warning signsInstall nonvehicular (animal) reflectorsInstall dynamic/variable accident warning signsInstall lane assignment signs

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 25All All 15 20All All 15 25All All 15 30

Night All All All 1 30

All Injury Rural 2-lane 5 -4 10 

All PDO Rural 2-lane 5 -5 7 

All All 15 25All All 15 13

Ped All 15 10

All All 15 22All All All All 1 25All All 15 18All All 15 25All All 15 25All Fatal/ Injury 15 18

All PDO 15 17

ROR All 15 27ROR All 15 27

All All 15 21All All <5,000/lane 15 37All All >5,000/lane 15 21All All All All 1 25All All 15 10All All 15 14All All 15 25

Fixed 

object All <5,000/lane 15 36

Fixed 

object All >5,000/lane 15 19

ROR All <5,000/lane 15 41

Improve pavement friction (grooving)

PAVEMENT

Improve pavement frictionInstall post-mounted delineators (tangents and curves combined)Improve pavement friction (groove shoulder)Install post-mounted delineators (curves)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

ROR All >5,000/lane 15 40

Overturn All <5,000/lane 15 54Overturn All >5,000/lane 15 35

Rear-end All <5,000/lane 15 54Rear-end All >5,000/lane 15 35

Wet 

pavement All 15 60

Wet 

pavement All <5,000/lane 15 64

Wet 

pavement All >5,000/lane 15 54

Wet 

pavement All All All 1 60

Wet 

pavement All All All 1 45

Wet 

pavement

Fatal/ 

Injury Rural 2-lane 38 30

All All <5,000/lane 15 13All All >5,000/lane 15 20

Fixed 

object All <5,000/lane 15 43

Fixed 

object All >5,000/lane 15 34

Head-on All <5,000/lane 15 43Head-on All >5,000/lane 15 61Head-on Fatal/ Injury 15 19

Head-on PDO 15 30

Left-turn Fatal/ Injury 15 41

Left-turn PDO 15 34

ROR Fatal/ Injury 15 28

ROR PDO 15 29

Rear-end Fatal/ Injury 15 12

Improve pavement friction (grooving) (cont'd)Improve pavement friction (overlay)Improve pavement friction (increase skid resistance)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Rear-end PDO 15 21

Rightangle Fatal/ Injury 15 11

Rightangle PDO 15 31

Sideswipe All <5,000/lane 15 43Sideswipe All >5,000/lane 15 61Sideswipe Fatal/ Injury 15 12

Sideswipe PDO 15 27

Wet 

pavement All <5,000/lane 15 23

Wet 

pavement All >5,000/lane 15 50

All All 15 17All All 15 10All All 15 24

Head-on All 15 86

Wet 

pavement All 15 51

Improve pavement friction (resurface with deicing additives)

Head-on All 15 31

All All 15 75

Fixed 

object All 15 93

Head-on All 15 90

Sideswipe All 15 90

Wet 

pavement All 15 91

23 Right- angle All 15

Improve pavement friction (overlay) (cont'd)Improve pavement friction (curve overlay)Improve pavement friction (resurface with open-graded mix)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Improve pavement friction (skid treatment with overlay)

Ped Fatal/ Injury 15 3

All All Rural 2-lane 5,000-22,000 5 14

5 

All Injury Rural 2-lane 5,000-22,000 5 15

8 

Head-on All Rural 2-lane highway 26 55 

Head-on Fatal Rural 2-lane highway 26 68 

Head-on Injury (minor) Rural 2-lane highway 26 26 Head-on Injury (major) Rural 2-lane highway 26 33 

Head-on/ 

Sideswipe All Rural 2-lane 5,000-22,000 5 21 12 

Head-on/ 

Sideswipe Injury Rural 2-lane 5,000-22,000 5 25 15 

Install or upgrade curbing

Fixed 

object All 15 50

All All Rural Multilane divided 8 16 

All Injury Rural Multilane divided 8 17 

ROR All Rural 2-lane >4,000 41 13 8ROR All Rural Multilane divided 8 10 ROR All Rural Highway 16 27 22 ROR All All Freeway 19 18 7

ROR All Rural Freeway 19 21 10

Install centerline rumble stripsInstall shoulder rumble strips

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

ROR All Rural All 57 34ROR All Rural Arterial 57 16ROR All Rural Between 

ramps

57 34

ROR All Rural Highway 57 38ROR All Rural Three-lane 57 36ROR All Rural 2-lane 57 32ROR Fatal/ Injury Rural 2-lane >4,000 41 18 12

ROR Injury Rural Multilane divided 8 22 

ROR Injury All Freeway 19 13 12

ROR Injury Rural Freeway 19 7 16

Install shoulder rumble strips on illuminated highways

ROR All Rural All 57 41

Install shoulder rumble strips on unilluminated highways

ROR All Rural All 57 31

All All 15 15

Head-on All 15 86

Night All 15 62

Vary centerline rumble strip width All All Rural Rural Highway 6 12 6

All All Rural Rural Highway

6

All All Freeway 6

100(1-(-0.07Pi+1.0)); Pi=proptype subset (for values of Pi, rsource).100(1-(-0.12Pi+1.0)); Pi=propinfluential crashes that occur otype i

Pave shoulderVary shoulder rumble stripsInstall shoulder rumble strips (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Delineate multiple lanes (painted lane lines) All All Urban Multilane 13 18 22 

All All 15 33All All All All 1 36All All 15 35All All 15 30All Injury All 2-lane 13 1 6 

All PDO All 2-lane 13 -1 5 

All All Urban 18 38 6 

All Injury Freeways 5 56 26 

All All Rural Undivided 1,000-4,000 2 -3 21 

All Injury All All 13 24 11 

Install edgelines, centerlines and delineators

All Injury All All 13 45 11 

All All <5,000/lane 15 44All All >5,000/lane 15 38All All All All 1 20All All 15 24All All 15 30All All 15 4All All 15 15All All 15 15All All 15 25All Injury 15 15All PDO 15 8

Fixed 

object All <5,000/lane 15 66

MARKINGS

Install centerline markingsInstall edgeline markingsInstall edgelines and centerlinesInstall chevron converging pattern markings on pavement

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Fixed 

object All >5,000/lane 15 59

ROR All 15 30ROR All All All 1 25

Overturn All <5,000/lane 15 45Overturn All >5,000/lane 15 50

Rear-end All <5,000/lane 15 45Rear-end All >5,000/lane 15 50

All Injury Rural 2-lane 13 3 4 

All PDO Rural 2-lane 13 3 11 

All Injury Rural 2-lane 13 -5 8 

All PDO Rural 2-lane 13 1 15 

Night All Rural 4-lane freeway

≤20000 4 -13 14 

Night All Rural 4-lane freeway <60000 4 33 21 

Night All Rural 4-lane freeway 20,001- 60,000 4 6 21 

Night All Rural 2-lane, DOC>3.5

≤5,000 4 -43

9 

Night All Rural 2-lane, DOC>3.5 5,001-15,000 4 -26 10 Night All Rural 2-lane, DOC>3.5 15,001- 20,000 4 -3 11 Night All Rural 2-lane, DOC<3.5

≤5,000 4 -16

3 

Night All Rural 2-lane, DOC<3.5 5,001-15,000 4 1 5 Night All Rural 2-lane, DOC<3.5 15,001- 20,000

4 24

7 

Install raised pavement markers (snowplowable) where DOC = Degree of CurvatureInstall edgeline markings (8 in) Install edgeline markings (cont'd)Install edgeline markings (from 4 to 6 in)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All 15 53

Head-on All 15 40

Sideswipe All 15 40

All All All All 40 -7 

Fatal/injury All All All 40 -5 

Lower posted speed by 5 mph All All All All 40 -44 

Lower posted speed by 10 mph All All All All 40 7 

Lower posted speed by 15-20 mph All All All All 40 5 

All All Urban Arterial (64ft) 30,000 5 42 8 

All All 15 22All All 15 8All All 15 35All Injury Urban Arterial 5 20 5 

All Injury Urban Arterial (64ft) 30,000 5 35 14 All PDO Urban Arterial 5 27 2 

All PDO Urban Arterial (64ft) 30,000 5 48 1 

Fixed 

object All 15 40

All All All All 40 11 

Fatal/injury All All All 40 7 

Raise posted speed by 5 mph All All All All 40 8 Install no-passing line

REGULATORY

Lower posted speedProhibit on-street parkingRaise posted speed

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Raise posted speed by 10-15 mph All All All All 40 15 

All Fatal All All 5 17 5 All Injury All All 5 7 3 All PDO All All 5 5 4 All Fatal All All 5 32 9 All Injury All All 5 15 5 All PDO All All 5 10 8 All Fatal All All 5 44 14 All Injury All All 5 22 8 All PDO All All 5 15 12 

Vary curb parking extent All All Urban Urban Street 6

100(1-(1+Ppk(Bpk-1))), Bpk=(1.10+0.365Iu2+0.609Pb1.0)Pap+1.0); Ppk=proportion segment length with parallel oparking (=0.5 Lpk/L), Lpk=curallocated to parking (mi), Iu2=variable for cross section(1 fostreet; 0 otherwise), Pb/o=for street with parking, the proporbusiness or office as an adjacfap/pp=ratio of crashes on streparking to those on streets witparking, Pap= for that part of tparking, the proportion with an

Reduce mean speed by 5% through speed limit change and enforcementReduce mean speed by 10% through speed limit change and enforcementReduce mean speed by 15% through speed limit change and enforcement

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All All Freeway 6All All Urban Urban Street 6All All All All 1 25All All 15 23All All 15 20All All 15 25All Fatal All Freeway 5 73 71 

All Fatal All Highway 5 69 36 

All Fatal Rural Highway 5 73 72 

All Fatal Urban Highway 5 63 52 

All Injury All Freeway 5 27 12 

All Injury All Highway 5 28 6 

All Injury Rural Highway 5 20 12 

All Injury Urban Highway 5 31 7 

All PDO All Freeway 5 32 26 

All PDO All Highway 5 18 7 

All PDO Rural Highway 5 30 43 

Improve lighting

100(1-EXP(-0.012(V-55))); V=(mph)

Vary speed limit

LIGHTING

100(1-((EXP(0.252IV<=30+0.318IV>road+1.15((V^2.066)(Exp(-0.0

road)))); Poff-road=proportion that occur off the roadway, for IV<=30 and IV>=45, refer to s(EXP(b(V-40)))); b= vary per rV=Speed limit (mph).

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All PDO Urban Highway 5 16 8 

Night All 15 37Night All 15 20Night All 15 45Night All 15 45

All All 62 6

All Injury 62 8

Night All 62 20Night Injury 62 29

All All All All 27 50 17 

All Fatal/ Injury All All 27 26 38 

All All All 27 8 16 

All All All 1 34 All All 15 30 All All 15 25 All All 15 35 

All All 15 34 All All 15 25 

Add two-way left-turn laneImprove lighting (cont'd)Install lighting at interchangesInstall lighting

OPERATIONAL

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

All Fatal/ Injury All 27 20 25 

All Injury 15 20 

All PDO 15 35 

Head-on All 15 36Head-on Fatal/ Injury 15 67 

Head-on PDO 15 64 

Left-turn All 15 33Left-turn All 15 33 

Left-turn Fatal/ Injury 15 17 

Left-turn PDO 15 38 

ROR All 15 37ROR Fatal/ Injury 15 90 

ROR PDO 15 16 

Ped All 15 19

Rear-end All 15 36Rear-end All 15 36 

Rear-end All 15 36 

Rear-end Fatal/ Injury 15 32 

Rear-end PDO 15 38 

Rightangle All 15 20 

Rightangle Fatal/ Injury 15 31 

Add two-way left-lane (cont'd)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Rightangle PDO 15 23 

Sideswipe Fatal/ Injury 15 32 

Sideswipe PDO 15 37 

All All 15 43All All All All 1 33

Implement crossover at work zone All All 4-lane divided 6,800-38,000 12 0 

Head-on All 15 31

Left-turn Fatal/ Injury 15 37

Left-turn PDO 15 13

ROR Fatal/ Injury 15 19

ROR PDO 15 30

Ped Fatal/ Injury 15 33

Ped PDO 15 42

Rear-end Fatal/ Injury 15 21

Rightangle Fatal/ Injury 15 16Rightangle PDO 15 23

Sideswipe PDO 15 29

Implement single lane closure at work zone All All 4-lane divided 20,000- 41,500 12 -56 

All All 15 32All All All All 1 20All All 15 20

Wet 

pavement All 15 40

Implement maintenance and bituminous overlayAdd two-way left-lane (cont'd)Convert from two-way to one-way trafficImprove drainage patterns

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Ped All 15 74Ped All 15 75Ped All 15 89Ped All 15 65Ped All 15 65Ped All 36 88

All All 2-lane 15 32All Injury 2-lane 15 59

Left-turn All 2-lane 15 46

Rear-end All 2-lane 15 46

Sideswipe All 2-lane 15 46

All All Urban Freeway 77,000- 126,000

5 -11

5 

All Fatal/ Injury Urban Freeway 77,000- 126,000 5 -11 8 

All

Fatal/ 

Injury/ 

PDO

Urban Freeway 77,000- 126,000

5 -10

7 

All All Urban Freeway 77,000- 126,000

5 -3

8 

All Fatal/ Injury Urban Freeway 77,000- 126,000 5 -7 13 

All

Fatal/ 

Injury/ 

PDO

Urban Freeway 77,000- 126,000 5 -4 11 

Reduce driveway density (general) All All Urban Urban Street 6Remove unwarranted signals (one-way streets) Ped All 46 17

Vary passing lanes All All Rural Rural Highway

6

Reconfigure lanes within existing pavement width (five to six in one direction)Reconfigure lanes within existing pavement width (four to five in one direction)

0.25 for one direction with threfor two direction with four lane100(1-(EXP(0.008(Dd,b/o-50)density of driveways serving boffice land uses (driveways/m

Reconfigure lanes within existing pavement width (two to three in one direction)Install sidewalk (to avoid walking along roadway)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors Roa

Daily Traffic 

Volume 

(veh/day)

Road Type 

Crash Type Countermeasure(s) Area Type Crash Reduction Factor / Function Crash Severity 

Effectiveness

Ref Std 

Erro

Vary truck presence All All Urban Urban Street 6

100(1-((ftk-1.0)(1-Poff-road)+1ftk=(2EXP(-0.059Pt)+0.017Pt)road=proportion of crashes throadway, Pt=percent of truck 100(1-(1.0+Truck/Basei)), for Truck and Basei, refer to sour

FHWA-SA-08-011 September 2008 
Tables for Pedestrian Crash Reduction Facto
Table 10: Signalization Countermeasures
Desktop Reference for Crash Reduction Factors 

Add exclusive pedestrian phasing Pedestrian All 28 34 

All All 62 1 7

Left-turn All 62 99 1

All All 62 0 

Left-turn All 62 16 2 

All Fatal/Injury 49 12 9

Pedestrian Fatal/Injury 49 37

Replace existing WALK / DON'T WALK signals with pedestrian countdown signal heads

Pedestrian Fatal/Injury Urban (San Francisco) 32 25

All All 15 20

Pedestrian All 15 53Pedestrian All 5 0

All All 15 25All All 15 15

Pedestrian All 15 55Pedestrian All 15 50

Modify signal phasing (implement a leading pedestrian interval)

Pedestrian All 28 5

Remove unwarranted signals (one-way street) Pedestrian All 46 17

Convert permissive or permissive/protected to protected only left-turn phasingConvert permissive to permissive/protected left-turn phasingInstall pedestrian signal

Countermeasures

SIGNALIZATION COUNTERMEASURES

Improve signal timing [to intervals specified by the ITE Determing Vehicle Change Intervals: A Proposed Recommended Practice (1985)]

Obs

Effectiven

Crash Reduction Factor / 

Function

Crash Type Crash Severity Area Type Std Error Ref 

FHWA-SA-08-011 September 2008 
Table 11: Geometric Countermeasures
Desktop Reference for Crash Reduction Factors 

Countermeasures Obs

Effectiven

Crash Reduction Factor / 

Function

Crash Type Crash Severity Area Type Std Error Ref 

Convert unsignalized intersection to roundabout Pedestrian Fatal/Injury Urban 11 27 12 

Convert intersection to roundabout Pedestrian All 55 89

Pedestrian All 15 86Pedestrian All 1 14 90 Pedestrian Fatal/Injury 15 90Pedestrian PDO 15 90Pedestrian All 15 100Pedestrian All 15 67Pedestrian All 15 5Pedestrian All 15 90

Install pedestrian overpass/underpass 

(unsignalized intersection)

Pedestrian All 28 13

Install raised median Pedestrian All 15 25Install raised median (marked crosswalk) at unsignalized intersection

Pedestrian All 60 46

Install raised median (unmarked crosswalk) at unsignalized intersection

Pedestrian All 60 39

Install raised median (unsignalized intersection) Pedestrian All 28 69

All All 5 30 67 All Fatal/Injury 5 36 54 

Pedestrian All 28 8

Install refuge islands Pedestrian All 28 56

Pedestrian All 15 74Pedestrian All 36 88 

GEOMETRIC COUNTERMEASURES

Install raised pedestrian crossingInstall pedestrian overpass/underpassInstall sidewalk (to avoid walking along roadway)

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Countermeasures Obs

Effectiven

Crash Reduction Factor / 

Function

Crash Type Crash Severity Area Type Std Error Ref 

Pedestrian All 15 75Pedestrian All 15 89Pedestrian All 15 65Pedestrian All 15 65

Narrow cross section (4 to 3 lanes with two way left-turn lane)

All All Urban 62 29 2 

Provide paved shoulder (of at least 4 feet) (to avoid walking along roadway)

Pedestrian All 15 71

Install sidewalk (to avoid walking along roadway) (cont'd)

FHWA-SA-08-011 September 2008 
Table 12: Signs / Markings / Operational Counterm
Desktop Reference for Crash Reduction Factors 

Countermeasures Obs

Effectiven

Crash Reduction Factor / 

Function

Crash Type Crash Severity Area Type Std Error Ref 

All All 62 4

All Injury 62 6

Night All 62 21

Night Injury 62 29

All All 62 6

All Injury 62 8

Night All 62 20

Night Injury 62 29

Pedestrian All 15 39Pedestrian All 21 69 19

Pedestrian All Urban 30 39 Pedestrian Fatal 13 78 87 Pedestrian Injury 13 42 18 

Improve pavement friction Pedestrian All 15 10Improve pavement friction (skid treatment with overlay) Pedestrian Fatal/Injury 15 3Add intersection lightingAdd segment lightingImprove lighting at intersectionsConvert two-way to all-way STOP control

SIGNS / MARKINGS / OPERATIONAL COUNTERMEASURES

FHWA-SA-08-011 September 2008 
Desktop Reference for Crash Reduction Factors 

Countermeasures Obs

Effectiven

Crash Reduction Factor / 

Function

Crash Type Crash Severity Area Type Std Error Ref 

Increase enforcement related to motorist yielding in marked crosswalks combined with a public education campaign

Pedestrian All 63 23

Increase enforcement to reduce speed Pedestrian All 28 70Install far-side bus stops (signalized intersection) Pedestrian All 28 1Install object markers Pedestrian All 15 29

All All 15 18All All 15 15All All 15 20All All 15 15All All 15 20

Pedestrian All New Orleans 5 -81 88 

Pedestrian All New York 5 -43 24 Pedestrian All Ohio 5 -57 31 Pedestrian All Wisconsin 5 -108 51 

All All Urban/ Suburban 62 

Prohibit left-turns Pedestrian All 15 10Remove marked unprotected crosswalks from arterial intersections

Pedestrian All Urban 5 73

Restrict parking near intersections (to off-street) Pedestrian All 15 30Permit right-turn-on-red

100(1-(0.984)^n); n=number of sigintersection appraoches where RTprohibited

Install school zone warning signs

FHWA-SA-08-011 September 2008 
September 2008 

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(1996)

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8 Carrasco, O., McFadden, J., and Chandhok, P., "Evaluation of the Effectiveness of Shoulder Rumble Strips 

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Washington, D.C., Transportation Research Board of the National Academies, (2007) pp. 29-31.

10 Clark, J. E., Maghsoodloo, S., and Brown, D. B., "Public Good Relative to Right-Turn-on-Red in South Carol

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September 2008 

17 Gates, T. J., Noyce, D. A., Talada, V., and Hill, L., "The Safety and Operational Effects of "Road Diet" Conve

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2007 TRB 86th Annual Meeting: Compendium of Papers CD-ROM, Vol. TRB#07-2762, Washington, D.C., (2

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28 Institute of Transportation Engineers, "Toolbox of Countermeasures and Their Potential Effectiveness to Ma

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29 Lee, J. C., Wortman, R. H., Hook, D. J., and Poppe, M. J., "Comparative Analysis of Leading and Lagging Le

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31 Lyon, C, Haq, A., Persaud, B. N., and Kodama, S. T. , "Development of Safety Performance Functions for S

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46 Persaud, B., Hauer, E., Retting, R. A., Vallurupalli, R., and Mucsi, K., "Crash Reductions Related to Traffic S

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48 Preston, H. and Schoenecker, T., "Bypass Lane Safety, Operations, and Design Study" MN/RC-2000-22, St

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49 Retting, R. A., Chapline, J. F., and Williams, A. F., "Changes in Crash Risk Following Re-timing of Traffic Sig

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50 Rodegerdts, L. A., Blogg, M., Wemple, E., Myers, E., Kyte, M., Dixon, M., List, G., Flannery, A., Troutbeck, R

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Report No. FHWA-SA-08-011 

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