Targeted Reporting of Speeding-Related Crashes

ARIZONA DOT

ISSUE STRATEGIES TAKEAWAYS

➤ Coding of Speed Too Fast

for Conditions on crash forms

may include impaired/weather

related crashes

➤ Situations exist where no speed is

safe and may be better addressed

by countermeasures other than

those targeted to speeding

➤ Data-driven approach

➤ Acknowledged variability in

coding crash forms

➤ Updated coding instructions to

provide more concrete guidance

➤ Speeding-related locations can be

identified

➤ Countermeasures can be targeted

to the cause of crash (speeding

versus impairment) allowing

better allocation of resources

➤ More consistency in coding

Around one-third of Arizona fatal crashes were coded as 

speeding related between 2012 and 2016 and over 53 percent 

of those fatal crashes were also coded as impaired but below 

the posted speed limit1,2,3. 

Correcting the interpretation of behavioral conditions would 

have removed crashes such as DUI (53 percent), distracted 

(4 percent), sleeping or fatigued (3 percent) that were not 

marked as exceeding the posted limit and where no speed 

would have otherwise been reasonable. This would have 

reduced the number of crashes during this period that were 

coded as speeding related (Speed exceeded the limit and 

STFC) from over 33 percent down to approximately 11 percent 

of total fatalities.

As a result, Arizona made the decision to address the issue 

by providing clear instructions and training that would 

remove DUI and other impaired crashes from the category of 

STFC. In this manner locations with actual speeding-related 

issues can be better targeted1. 

Speeding Vehicle. Source: Getty Images

1 FHWA-SA-20-082

Background

Speed Too Fast for Conditions (STFC) is a field provided 

on most agency crash forms. The intent is to label scenarios 

where a driver was traveling below the posted speed limit but 

the speed at the time of the crash was not appropriate for 

prevailing environmental conditions and was a contributor to 

the crash. However, significant variations exist in interpreting 

the definition of the environment when coding crash forms. As 

a result, it is often left to the attending officer’s interpretation. 

The Problem

In Arizona, historically STFC was defined as “Traveling at a 

speed that was unsafe for the road, weather, traffic or other 

environmental conditions at the time.” In many cases, an 

officer would include the behavioral or human environment 

and could interpret driver incapacity (Driving Under the 

Influence (DUI), impaired, distracted, fatigued) as a condition 

that would warrant traveling at a lower speed regardless of 

actual roadway conditions. For instance, a drunk driver on dry 

daytime roads traveling under the speed limit could be coded 

as Speed Too Fast for Conditions if the officer felt the state 

of impairment warranted a lower speed. Depending on the 

attending officer’s interpretation, there may be scenarios in 

which no speed is safe for conditions1.

While it is important to address these crashes, solutions 

should focus on the root cause of the crash when feasible. 

Countermeasures geared specifically towards speeding, such 

as Dynamic Speed Feedback Signs (DSFS), lane narrowing, or 

use of landscaping, may be less effective when the driver is 

impaired. Rather areas with a high number of impaired 

crashes should be targeted with countermeasures that 

address the impairment, such as enforcement.

Case Study 6: Noteworthy Speed Management Practices
Targeted Reporting of Speeding-Related Crashes

Redefining “Speeding-Related”

Arizona adapted coding instructions for their crash form for 

the field Speed Too Fast for Conditions. The new instructions 

define STFC as the following:

“Traveling at a speed that was unsafe for the road, 

weather, traffic or other environmental conditions at 

the time. This does not include behavioral conditions 

such as distraction, impairment, fatigue, falling asleep 

or other violations that would otherwise make any 

speed unreasonable”. 

Based on the new instructions, crashes where impairment, 

fatigue, or other behavioral issues are the main contributor 

are coded as impairment. Crashes with an impaired driver can 

still be coded “Exceeding the Posted Speed Limit” when both 

conditions are met1.

In the future, officers and agencies will be able to use the data 

to identify locations with a high number of speeding-related 

crashes which actually represent a speeding problem. In this 

manner, automated enforcement and other speeding-related 

countermeasures can be applied and are expected to be more 

effective. For instance, ADOT is evaluating speed limit decals 

on State Route 347 where a review of crash reports indicated 

drivers were cited as STFC in more than half of crashes along 

this section of roadway4.

Percentage of fatal crashes 

coded as STFC decreased by 

more than 1/3 after changing the 

crash form instructions.

Fatal Crashes in Arizona. 

Data Source: King, 2018; ADOT, 2016

53%

23%

17%

4% 3%

DUI

Other STFC

Exceeding 

Posted

STFC & Distracted STFC & Fatigued

Officer uses driver information to complete a traffic ticket. Source: Getty Images

FHWA-SA-20-082

2

Case Study 6: Noteworthy Speed Management Practices
Targeted Reporting of Speeding-Related Crashes

Key Takeaways and Lessons Learned

Addressing crash contributing factors to target 

countermeasures – Although both Speed Too Fast for 

Conditions and Exceeded the Posted Speed Limit represent 

important safety issues, in most cases they represent two 

vastly different situations. In many cases, STFCs are either 

impaired drivers or weather related situations. Since neither 

scenario is usually tied to a specific roadway section, it 

is difficult to target site-based countermeasures. More 

importantly, many speed management countermeasures may 

not be suited to the problem. For instance, DSFS or safety 

cameras are set to activate at speed thresholds set for dry 

conditions. As a result, an impaired driver involved in a crash 

or a driver traveling too fast for weather conditions could be 

coded by the attending office as STFC yet be traveling below 

the thresholds set to activate DSFS or safety cameras. This 

may lead to utilizing countermeasures which would have no 

impact on these types of crashes. Other speed management 

countermeasures, such as lane narrowing or pavement 

markings, may similarly not be well suited in these situations if 

drivers are cognitively impaired.

Arizona came to this realization as they considered how 

speeding-related crashes could be addressed. As a result, 

they found a solution that allows them to focus on the root 

cause of the crash when feasible. The ability to parse crashes 

by situations where speeding-related countermeasures are 

effective versus situations, such as impaired driving, where 

countermeasures such as targeted enforcement are effective is 

important because it allows agencies to better focus resources.

Consistency in coding – Arizona also made the decision to 

update the crash form rather than relying solely on additional 

training for officers in how to better code STFC. This was 

successful since, even with training, significant variation can 

exist in how officers interpret fields on a crash form. As a 

result, the updated crash form provides more consistency.

1 King, Jeff. Speeding Related Collision Data: It May Not Be Telling You What You Think Presentation at the 2018 FHWA Safety Discipline Seminar.

2 ADOT. 2015 Motor Vehicle Crash Facts for the State of Arizona Arizona Department of Transportation, 

Transportation Systems Management and Operations. June 2016. azdot.gov/sites/default/files/2018/10/2015-crash-facts.pdf

3 ADOT. 2018 Motor Vehicle Crash Facts for the State of Arizona. Arizona Department of Transportation, 

Transportation Systems Management and Operations. June 2019.

4 Giulliano, Tina. ADOT tests speed limit decals on highway pavement. AZFamily. Sept 20, 2019. 

https://www.azfamily.com/traffic/adot-tests-speed-limit-decals-on-highway-pavement/article_eccf35c6-dbfd-11e9-b81f-9b64df3e3fe2.html

Case Study 6: Noteworthy Speed Management Practices 3 FHWA-SA-20-082