March 9, 2018 BY Kathleen Ferrierin News, Safety Over Speed

Take Action to Update Outdated Speed Setting Practices

Give Input on Safety in New Survey

The Vision Zero Network lauded a landmark study released last summer by the National Transportation Safety Board (NTSB) that recognized the problem of speeding in the U.S. and called for stepped-up national leadership and modernization of speed management practices. In the study, NTSB prevailed upon many influential agencies to modernize speed practices, including updating the way speed limits are set to prioritize safety over speed, and enabling the use of proven speed control technologies like safety cameras.

We hope that a significant action this week shows that key federal agencies are listening to these much-needed recommendations.

This week, a little known yet influential group, the National Committee on Uniform Traffic Control Devices (NCUTCD), announced they are reviewing the language in the Manual on Uniform Traffic Control Devices (MUTCD) related to setting speed limits, and posted a survey asking for input on the NTSB findings as well as a variety of factors that influence the setting of speeds. The NCUTCD is an organization which largely controls the standards and design of traffic signs and signals across the U.S., as well as practices that guide traffic on streets and highways, e.g. speed limits. The MUTCD is the guide where influential roadway standards are encapsulated, a so-called “bible” among traffic engineers. It is maintained by the Federal Highway Administration but written by the NCUTCD.

This NCUTCD task force wants your input on the NTSB findings before advancing recommendations to the NCUTCD Council for future FHWA updates to the MUTCD. The findings will be utilized by the task force and shared with the profession following completion. The objective will be to have a recommendation to present to the NCUTCD technical committees in 2018. 

The survey is technical in nature, geared towards traffic engineers, but if you’re someone working in the transportation field, you should know about it, and familiarize yourself with the questions. And this is a chance to have input on an important process that influences Vision Zero progress across the country. No deadline is provided but the survey should be answered in a timely fashion to allow NCUTCD to report back with its findings.

Why This is Important to Vision Zero

NTSB’s speed study issued 19 recommendations. The ones being considered by NCUTCD are recommended changes to the MUTCD related to setting appropriate speed limits, which, if made, would better align the MUTCD with a Safe Systems Approach, the cornerstone of the Vision Zero movement.

Specifically, if the NTSB recommendations are enacted, the MUTCD would require that (a) factors such as surrounding land use and history of traffic injuries and deaths be considered as part of setting speed limits, and (b) the safe system approach be incorporated for urban roads “to strengthen protection for vulnerable road users”.

We encourage the NCUTCD to act on the recommendations in the NTSB study, particularly by modifying the long-held 85th percentile rule, the practice of setting a speed limit based on the speed at which 15% of motor vehicles are driving faster and 85% are driving slower, essentially allowing drivers to set their own speed limits.

Speed Setting Practices Date Back to 1940s-1960s

NTSB’s study connected this 85% standard back to the 1940s – 1960s when studies were carried out on rural roads with free-flowing traffic, a far cry from many multi-modal, urban roads today. Yet, the standard for rural roads with free-flowing traffic persists. It is not hard to understand that this long time practice leads to a cycle of higher speeds, as more people drive faster, the speed limit increases. As the NTSB study explained, the 85th percentile practice leads to “unintended consequences, leading to higher speeds, and hence, a higher 85th percentile speed.” Also problematic, the practice does not take into account surrounding land uses or the presence of other modes – including people walking and bicycling - on the road. At a time when far too many people are dying on U.S. roadways , on average 100 each day, updates to prioritize safety over speed within these outdated policies are critical.

"The 85th percentile practice leads to unintended consequences, leading to higher speeds, and hence, a higher 85th percentile speed.” - NTSB Speed Study

Much has been written about the devastating effects of 85th percentile with titles such as:

American Speed Limits are Based on 1950s ScienceThe 85th Percentile Rule is Killing UsSpeed Kills So Why Do We Keep Designing For It?

The NCTUCD survey provides the opportunity to tell national leaders that speed-setting practices should be updated, in line with a Safe Systems approach, to protect the safety of all roadway users. The Vision Zero Network is encouraged by this positive step and we commit to continue to prioritize safety over speed.

If you are a transportation engineer or transportation professional, we encourage you to take the time to take the survey. And for all in the transportation profession, take a look at the survey here.

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