REESTABLISHING TRUST IN SPEEDING-RELATED CRASH DATA 

When contemplating an approach to understand the myriad of complex 

and interwoven factors and circumstances involved in speeding-related 

questions, practitioners sometimes ask “Where do I even start?” and “Which 

data are the most trustworthy?”

State crash reports use a variety of categories to describe speeding-related 

crashes: “exceeded speed limit,” “too fast for conditions,” “following too 

closely,” “driving aggressively,” etc. The assignment of these categories 

may be based largely on the perceptions or judgment of the responding 

law enforcement officers, introducing the potential for human error. 

Compounding this concern is that crash report categories may be imprecise; 

for example, driving “too fast for conditions” may not accurately or fully 

describe the circumstances surrounding the crash. As a result of these factors, 

many transportation agencies do not believe their speeding-related crash 

data is truly reflective of actual events and suitable for addressing speedingrelated crashes. 

A Systemic Safety Approach uses information from well-documented severe 

crashes (fatal and serious injury crashes) to help agencies define where future 

crashes may occur. Severe crash records have a greater accuracy than lesser 

crash severity records increasing an agency’s certainty that these crashes are 

speeding-related and that the data are reliable. A Systemic Safety Approach 

uses severe crashes to identify the most prevalent crash types, facility types, 

and risk factors. This trilogy of characteristics enables an agency to identify 

locations with roadway characteristics similar to those of the known severe 

crash locations and preemptively prevent crashes from continuing to occur at 

those sites.

Improving Speed Management Using 

a Systemic Safety Approach

A Systemic Safety 

Approach

SPEED MANAGEMENT

Traditional crash 

analysis treats the 

problem after a crash 

has occurred.

A Systemic Safety Approach uses speeding-related severe crash data to identify locations 

with similar risk characteristic that may experience a severe crash in the future.

A Systemic Safety 

Approach fixes the 

problem before a 

tragedy occurs.

1
Step 1 Identify Focus Crash Types

 Step 2 Identify Focus Facilities 

96 Severe Crashes

Rural 

83 Severe Crashes 

(86%)

Undivided 

67 Severe Crashes 

(70%)

2 Lanes 

57 Severe Crashes 

(59%)

Urban 

13 Severe Crashes 

(14%)

Divided 

16 Severe Crashes 

(17%)

3 or more Lanes 

10 Severe Crashes 

(10%)

<35 MPH 

3 Severe Crashes

(14%)

55+ MPH 

15 Severe Crashes

(16%)

40-50 MPH 

29 Severe Crashes 

(30%)

Roadway Departure Horizontal Curve 

Speed-Related Severe Crashes

A BETTER WAY: SIX STEPS TO IDENTIFYING SPEEDING IMPROVEMENT OPPORTUNITIES

The following steps are based on the process outlined in the FHWA’s Systemic Safety Project Selection Tool.1 

SPEED MANAGEMENT • A Systemic Safety Approach

2

 1 Federal Highway Administration, “Systemic Safety Project Selection Tool,” FHWA-SA-13-019 (Washington DC: July 2013). 

Available at: https://safety.fhwa.dot.gov/systemic/resources.cfm.

Examine the agency’s speeding-related severe crash 

data to determine a focus crash type and select the 

crash type with the greatest number or greatest severity 

of crashes. Often, these crash types will be emphasis 

areas in a States’ Strategic Highway Safety Plan (SHSP). 

Examples include:

 Intersection crashes

 Fixed object crashes 

 Horizontal curve crashes

The purpose for identifying a focus facility type is to 

take a very broad crash type (e.g., horizontal curves) and 

break it down into smaller groups based on location 

types that exhibit similar risk characteristics. 

Consider representing this “narrowing down” as a crash 

tree diagram that graphically breaks down crashes into 

progressively more detailed categories. The highest 

level of the crash tree begins with the total number of 

severe crashes in the focus crash type. In the example at 

right, the focus crash type is Speeding-related Roadway 

Departure Horizontal Curve crashes. Each subsequent 

level separates the severe crashes by intrinsic roadway 

characteristics. The roadway characteristics with the 

greatest number of severe crashes are carried forward 

into the next level of the crash tree diagram. 

1

Note: Percentages in parenthesis represent the proportion of total 

roadway departure horizontal curve speeding-related severe crashes. 

(Total: 96 Severe Crashes).
3

 2 Federal Highway Administration, Potential Risk Factors, Washington, D.C. (n.d.). 

Available at: https://safety.fhwa.dot.gov/systemic/pdf/FHWA_SystemicApproach_PotentialRiskFactors.pdf.

 3 Federal Highway Administration, CMF Clearinghouse User Guide, Washington, D.C. Available at: http://www.cmfclearinghouse.org/userguide.cfm.

SPEED MANAGEMENT • A Systemic Safety Approach

Step 3 Gather Risk Factor Information 

The next step is to define, document, and assess the 

most common roadway characteristics, or risk factors, 

associated with the focus crash type and focus facility 

type. Again, an agency does not necessarily need a 

robust dataset to identify locations that can benefit 

from safety improvements. Examples of methods an 

agency can use to quantify roadway and intersection 

characteristics for risk factor evaluation include: 

 Roadway and intersection inventories

 Online aerial imagery

 Photo and video logs

 Field visits

It’s important to remember that a roadway feature 

itself is not the risk factor; rather, it is the degree to 

which the characteristic contributes to crash severity or 

frequency. For example, a 90 degree horizontal curve 

is more likely to contribute to a crash than a 5 degree 

curve. Translated: the 90 degree curve poses a greater 

risk for future crashes.

Step 4 Identify and Evaluate Risk Factors 

Identifying risk factors 

can largely come from 

engineering judgment and 

experience, but it can also 

come from documented 

resources, including the 

Highway Safety Manual

(HSM), field visits, 

conversations with field 

staff about their first-hand 

observations, and the 

Federal Highway Administration’s guide to Potential 

Risk Factors.2 

A few of the many examples of potential risk factors 

include:

 Number of lanes. 

 Lane/Shoulder/Clear zone width.

 Curve radius or density.

 Roadside edge features and quality.

 Traffic volume.

 Intersection elements.

 Speed limit or differential.

 Pavement condition.

Note that practitioners can use the Highway Safety 

Manual and the Crash Modification Factor (CMF) 

Clearinghouse3 to estimate the degree to which each 

risk factor contributes to the overall reduced level of 

safety within the facility type. 

Step 5 Apply Risk Factors to the Entire Focus Group Population to Identify a Ranked List of Sites

Expand the vetting process from the severe crash 

locations (used to determine the focus group and risk 

factors) to all roads within the focus facility type. For 

each crash location, determine the number of risk 

factors (determined in Step 4) the site exhibits. This can 

be accomplished by using a roadway or intersection 

inventory, online aerial imagery, photo or video logs, 

or field visits. Rank locations based on the number 

of risk factors present. Some agencies choose to use 

a weighted ranking system, emphasizing roadway 

characteristics with greater risk. The result will be a 

ranked list with severe crash locations near the top 

along with non-severe crash locations that have a 

high-risk of experiencing a severe crash in the future.

An Introduction to the

HigHway

Safety

Manual
http://safety.fhwa.dot.gov

FHWA-SA-18-051

Step 6 Select the Appropriate Countermeasure(s) 

Countermeasure selection should be largely based on the risk factors identified. For example, if a narrow 

shoulder is a risk factor, then a countermeasure may be expanding shoulder widths. Not all risk factors need to 

be directly addressable. For example, if a horizontal curve has narrow lanes, a tight radius, and no shoulders, then 

an appropriate countermeasure may be enhanced roadside delineation because it draws the motorist’s eyes to 

these features. Directly addressing a risk factor by widening the road or straightening a curve may not be cost 

effective. 

Once an agency has identified risk factors, it can consider the benefit-cost ratio of various countermeasures. The 

CMF Clearinghouse and other published resources can provide expected countermeasure safety benefits and the 

crash types they address.

AN EFFECTIVE, DATA-CENTRIC APPROACH

A Systemic Safety Approach does not require robust data or complex analysis methods to be effective. Nearly 

all transportation professionals have access to the basic data needed to pursue systemic safety analysis and 

make appropriate systemic-based decisions. By identifying recurring risk factors using speeding-related severe 

crashes, agencies can treat the most at-risk facilities throughout their system (e.g., intersections with similar 

characteristics, horizontal curves with a particular radius, etc.) occur using low-cost, effective speed-mitigation 

countermeasures.

For assistance, or to request technical support, 

contact:

Guan Xu

FHWA Speed Management Program Manager

Phone: 202-366-5892

Email: Guan.Xu@dot.gov

SPEED MANAGEMENT • A Systemic Safety Approach

Additional Information

For more information on a Systemic Safety Approach to Speed Management, visit:

 FHWA’s A Systemic Approach to Safety Website. This website contains Systemic Safety resources including the 

Systemic Safety Analysis Tool. (https://safety.fhwa.dot.gov/systemic/resources.cfm)

 FHWA’s Speed Management Website. This website contains Speed Management resources including examples 

of speed management plans and ongoing speed management research. (https://safety.fhwa.dot.gov/

speedmgt/)

4