There’s a reason that a stop sign in Sheboygan looks like a stop sign in Seattle. There’s a reason that road lanes are divided by white and yellow markings in both places too. There’s also a reason why, if a bicycle lane symbol etched on the street is accompanied by a word, like “SLOW,” the bicycle always comes first. The reason is 862 pages long and has been around, in one form or another, for 85 years: the Manual for Uniform Traffic Control Devices.

The idea behind the manual is that, for roads to be safe, they must be consistent, no matter where people are driving, walking, or scootering. The manual is “a visual representation of what the rules of the road are,” says Jeff Lindley, the deputy executive director of the Institute of Transportation Engineers. It won’t tell you when to put in a roundabout, but it will tell you the sign you need to help clueless drivers navigate a roundabout. “It's not a real fun evening bedtime read,” says Luke Schwartz, the transportation manager for the city of San Luis Obispo, California.

For transportation engineers, the manual is akin to a professional bible, which they consult weekly, if not daily. Inside is a mix of mandatory shalls, probably good shoulds, and OK-to-do mays. The Federal Highway Administration, the US Department of Transportation agency that has controlled what goes in the manual since 1971, maintains that engineers should always use their professional judgment to determine whether a particular road sign, lane marking, or bicycle stencil works for the situation.

Now the manual is getting its first update in 11 years. That’s brought out critics who say it is outdated and too focused on cars rather than people on foot or two wheels. Some city officials want the freedom to create traffic signs, markings, and street configurations that cater to their local roads, and the varied options—bus, moped, escooter—now available to their residents. They want the flexibility to choose different bike lane markings or to install colorful crosswalks, choices that are not endorsed by the manual. (Federal officials have issued sternly worded letters to cities including St. Louis, Ames, Iowa, and Lexington, Kentucky, urging them to bring creative crosswalks into compliance.) Earlier this year, several progressive transportation groups launched an effort to not just tweak the manual, but to reframe and rewrite it.

The tussle over an obscure set of federal rules points to a larger trend in transportation planning: a renewed focus on making streets equitable, climate-conscious, and safe for everyone, not just those in cars.

Nationwide, safety statistics are moving the wrong way. Preliminary data collected by the Governors Highway Safety Association found a 4.8 percent increase in pedestrian deaths last year. Factor in the reduced driving because of the pandemic and the number gets even more dire: a 21 percent increase in pedestrian deaths per vehicle mile traveled. That’s the largest jump since the government started keeping track of such numbers in 1975.

“This is the time to say, ‘What should the spirit of the document be? And what should be the best way forward?’” says Zabe Bent, the director of design at the National Association of City Transportation Officials, a group representing city departments of transportation in North America that is spearheading the effort to reframe the manual.

The Federal Highway Administration released a draft of proposed changes late last year. The last time the manual got an update, a few thousand people, mostly transportation professionals, submitted comments. This year, 26,000 comments poured in from all over the country.

Some arrived from big companies, including the ride-hail and mobility company Lyft, the Ford-owned scooter-share company Spin, and the Alphabet company Sidewalk Labs. Each asked for a major rewrite that would, as Sidewalk Labs put it, “more closely align with the equity, safety, and sustainability goals of American cities, as well as those of the Biden administration.”

Others came from individuals. “There’s a broader set of people who see that these streets don’t work, that there are too many people getting killed, that they’re too unpleasant. It’s not consistent with what a place or a community should be,” says Mike McGinn, a former mayor of Seattle and executive director of the group America Walks. He credits those everyday activists with the new interest in the design document—and his own group, which urged thousands of people to submit comments to the federal agency.

Some transportation engineers, meanwhile, wonder why their research-based traffic control device guidelines are receiving so much attention from people who don’t understand the inner workings of the profession.

Would an updated traffic control manual change the reality on the streets? Don Kostelec argues it would. Kostelec is a transportation planner and activist based in Boise, Idaho. In 2013 he backed a proposal to install a crosswalk across five lanes of a road managed by the state department of transportation. On one side of the proposed crosswalk was a residential area; on the other, a popular convenience store. As it was, people from the residential area who wanted to reach the convenience store safely had to walk more than half a mile to reach a signalized crosswalk. So often, the walkers would skip it, instead darting across traffic to pick up food. Kostelec asked the department to install a crosswalk, but was told, he says, that the proposal didn’t align with the manual’s recommendations. According to the manual’s guidelines, not enough people were crossing the dangerous road to warrant a new signal and crosswalk.

It was a classic chicken-and-egg problem—the crosswalk didn't exist, so not enough people were crossing to warrant a crosswalk, so the crosswalk continued to not exist. It was an example, Kostelec says, of local engineers “not getting any real leeway to use their engineering judgment.”

Consider how the manual instructs cities to set speed limits, the so-called 85th percentile rule. It recommends that agencies conduct occasional traffic studies to determine how fast drivers are traveling on a given road, then post a speed limit within 5 miles per hour of the 85th percentile speed—in effect, allowing speeders to establish the rules of the road. “The outcome is that we get roads that we have to sign at a higher speed than is the ideal, safe speed for that street,” says Schwartz, the San Luis Obispo official. It would be safer for everyone, he argues, if the manual “gave more flexibility for practitioners to design and manage streets based on the values and priorities of their cities.”

Technically, much of the manual’s guidance is not hard-and-fast rules. But planners hew closely to the guidelines for fear of legal trouble. If someone is hurt on a road that includes a design not endorsed by the manual, the city can find itself on the wrong end of a lawsuit. Some cities allow their engineers to deviate and apply for federal waivers from the rules, with pricey traffic studies and piles of documentation to back up their choices. But many others, especially small ones with small budgets, find diverging from the guidelines too risky. The manual is their North Star.

The last time the manual got an update, the process took more than a year; with the volume of comments this year, it may take longer. A spokesperson for the Federal Highway Administration says the agency “needs to carefully consider all comments before determining next steps and the timetable for updating the manual.” Given the interest, that might take a while.