Street Mural Trenton

A street mural on Centre St in Trenton. Street murals will be not allowed in the new MUTCD

The Federal Highway Administration is accepting public comments on the long overdue rewrite of the Manual of Uniform Traffic Control Devices (MUTCD). The manual is an important document as it standardizes signs and lane marking across the nation. However the existing MUTCD as written thwarts Vision Zero initiatives. The manual emphasizes speed and traffic flow at the expense of safety, especially for vulnerable road users.

“That’s not in the MUTCD” may be the most overused phrase in a combative transportation official’s vocabulary. The draft revision does little to improve the manual and some changes make it more onerous to put in safe bicycle and pedestrian facilities. In response, several national organizations and cities including Philadelphia are leading a campaign for a better and safer MUTCD.

The 85th Percentile of setting speed limits – On most roads speed limits are established based on what’s called the 85th percentile. The 85th percentile is the speed where 15% of the drivers are violating the speed limit. Then round it up to the nearest 5mph increment and that becomes the posted speed limit. Or to put it bluntly, record the speed of 10 drivers and set the speed limit to the 2nd most reckless driver. 

It gets worse. A neighborhood could complain that speeding is a problem in their neighborhood and demand that the DOT conduct a “speed study”. If the result is that more than 15 percent of the drivers are exceeding the speed limit, then the recommendation they will give will be to raise the speed limit. NACTO has a good writeup on the adverse cycle of using percentiles to determine speed limits.

Signal Warrants – Did you know that a road crossing with 99 pedestrians an hour and 4 pedestrian deaths in a year does not warrant a pedestrian signal? That’s what the MUTCD says. We don’t have a warrants for bridges based on the number of cars driving through a river. Signal warrants also ignore known conflicts such as the complicated turning vehicle patterns at large intersections. The Manual limits the installation of traffic signals because of the potential that they will slow car travel, and, as result, the guidelines place pedestrians at risk of being injured or killed. Here is a story that demonstrates how signal warrants can hurt the most vulnerable populations

Other Flaws in the New Manual

Poison Pills for Bike Lanes – New and more stringent language for bike lanes could make many existing facilities obsolete and make them more difficult to to install. 

Urban Traffic Control Devices – Traffic control devices appropriate for urban contexts, such as red transit lanes and pedestrian safety measures, are subject to high standards of testing.

Prohibition of Street Murals – New language stipulates that “the right-of-way is dedicated exclusively to highway-related functions” and that people should not be encouraged to “engage” with the street. Street mural often have a traffic calming effect

Accountability of Automated Vehicles – It is too early in the development of Automated Vehicles to be included in the MUTCD. The proposed language of the MUTCD could push cities to cater to AV’s instead of pushing AV developers to design vehicles to protects bicyclists and pedestrians..

Take Action – The deadline for submitting comments is May 14th. The easiest way to submit comments is to go to this link at Transportation for America

If you want to compose your own letter you can submit it here.

Read what others organizations have submitted:
City of Philadelphia
Toole Design Group (Very Detailed)
America Walks

New bike facility graphics in the MUTCD. While these additions are welcome some critics believe that some design requirements may make existing bike lanes obsolets.

New bike facility graphics in Chapter 9 of the MUTCD. While these additions are welcome critics believe that new design requirements may make the installation of bike lanes more difficult.


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