Booked on Planning
Booked on Planning
Rewriting Our Nation's Deadly Traffic Manual
Ever heard of the MUTCD? Most have not, but this influential document has been shaping U.S. road design since 1935, often prioritizing vehicle flow at the expense of pedestrian safety. We break down the controversial 85th percentile rule, which can lead to increased speed limits, and discuss how the MUTCD hinders creative urban design solutions like decorative crosswalks through our review of Sarah Bronin and Gregory Schill's article Rewriting the Nation's Deadly Traffic Manual. With roadway deaths on the rise, hear our critical arguments for reforming this manual to strike a better balance between traffic efficiency and the safety of all road users.
Show Notes:
- Read the full article at https://harvardlawreview.org/forum/vol-134/rewriting-our-nations-deadly-traffic-manual/
- To view the show transcripts, click on the episode at https://bookedonplanning.buzzsprout.com/
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you're listening to the booked on planning podcast, a project of the nebraska chapter of the american planning association. In each episode, we dive into how cities function by talking with authors on housing, transportation and everything in between. Join us as we get Booked on Planning. Welcome back, bookworms, to another episode of Booked on Planning. We're continuing the conversation on traffic engineering and narrowing into a part of our conversation that we had with Wes Marshall on traffic engineering manuals. In 2021, sarah Bronnan and Gregory Schill authored Rewriting Our Nation's Deadly Traffic Manual, which was published in the Harvard Law Review. The manual in question is the manual on uniform traffic control devices for and Highways, often shorthanded just to the MUTCD and, more often than not, the bane of my existence amongst a number of other planners, I'm sure. This 800-page document contains engineering guidance on everything from the rule that stop signs are to be read to how to set speed limits with a very questionable method. As you would have heard in listening to Wes on our last episode, this manual is very much vehicle-specific and flow-first safety and mobility.
Jennifer Hiatt:Last, I really appreciated that this article was written from a legal perspective. Sarah Bronin is a planner and a lawyer who teaches at Cornell, both in the School of Architecture, art and Planning and the law school, and her co-author, gregory Schill, teaches at the Iowa College of Law and the Iowa College of Engineering. So it's kind of an interesting perspective that I don't think we've really heard or seen from in the transportation world at this point. So over and over again, as we were talking with Wes, I kept thinking about how transportation engineers keep falling back on the MUTCD as their legal backstop. But there are plenty of other legal arguments to protect any rational decision made by a professional in the course of their professional duties.
Stephanie Rouse:Yeah, very interesting connection there. So the MUTCD dates back to 1935, when the Federal Highway Administration adopted it as a guide for the fledgling field of traffic engineering. Barely into its first few decades of existence, it's now in its 11th iteration, although adoption is pending in many states. This manual has incredible power in how we design our cities and can result in dangerous street designs and hostile environments. You may have never heard of this manual, but if you've ever been told that your community can't install a pedestrian crossing or paint a crosswalk a fun design, this document is what's prohibiting that improvement I always got so confused why you couldn't do a fancy crosswalk.
Jennifer Hiatt:That's some of the most iconic art you've ever seen, like the beatles walking across abbey lane and a really cool crosswalk and whatever. Like what is that? And in many ways it makes a lot of sense to have a manual like the mutcd. The united states is a large country and it would cause complete chaos if every state had its own set of regulation. It would be very dangerous if green means go in Nebraska but it means stop in Colorado. So it makes sense to have something that's overarching, and having the uniformity that's laid out in the MUTCD is important and if the manual had stopped there it would be a useful document. But unfortunately it goes significantly further, as you've said and we talked about with Wes, and it has massive reaching impacts on the MUTCD, while still not a well-known document to the masses, actually became more well-known.
Stephanie Rouse:during its 2020 update to the 11th edition, the Federal Highway Administration proposed revisions that garnered over 26,500 public comments. Not only transportation engineers, but many varied advocacy groups spoke out against the document, which had minimal improvements, and would, as the authors put it, against the document, which had minimal improvements and would, as the authors put it, quote perpetuate some longstanding, arbitrary, capricious or discredited rules, even as it introduced new ones bearing the same defects. It does this because it puts vehicle flow first, at the expense of the safety of pedestrians, bicyclists, transit users and other vulnerable road users.
Jennifer Hiatt:Arbitrary and capricious is the legal kiss of death for cities, so maybe we should be considering better alternatives here. This version of the manual, like many before it, states that its purpose is to establish national criteria for the use of traffic control devices that meet the needs and expectancy of road users on all streets, highways, bikeways and site roadways open to public travel. But then it turns around and primarily considers road users to be drivers of automobiles only, and that bias shows up in every part of the manual and is really the most frustrating part about it.
Stephanie Rouse:One main section of the manual that highlights this car bias is the 85th percentile rule, which justifies speed limits to create free-flowing traffic. The method looks at what speed is traveled at the 85th percentile of drivers on a roadway, then sets the speed accordingly, effectively making the speed what the driver traveling faster than 85% of other cars is going, instead of designing a road for traffic speeds that are safe for the environment and then setting the speed limit accordingly. It also gives traffic engineers the ability to raise the speed limit, even if it would increase safety concerns to legalize the speeding of those 15% of drivers on a roadway. It in effect delegates the interpretation of the law to the small group of drivers violating it the worst.
Jennifer Hiatt:Yeah, it's such a perverse incentive. Instead of rewarding the people who go at or below the posted speed limit, we are rewarding those who willfully break a posted law. It's allowing the actions of the few to endanger the majority, and it doesn't make sense. Additionally, it already erases the needs or interests of anyone that's actually not in a car. When we should be encouraging multimodal transportation options, we are instead not even taking them into consideration in one of the most influential guidelines on traffic speed out there.
Stephanie Rouse:The primary focus of the manual is to increase traffic speeds and reduce traffic congestion, a function realized during the pandemic, when remote work and lockdowns were prominent. What the article points out, though, is when this was finally achieved. It proved deadly, with 2020 as the highest year-over-year increase in roadway death rates on a per-mile travel basis in 96 years. So you would think, seeing this, that the manual would need a drastic shift in focus from moving cars fast and freely to slowing them down and prioritizing other modes of travel. Sadly, that's not what took place in the 11th edition update. Changes were made, but not the large-scale, impactful changes that were needed.
Jennifer Hiatt:It is unfortunate that the Federal Highway Administration has already adopted the 11th version. I understand that they went through the proper promulgation of rules and procedures, but it seems to me that a larger discussion with multiple parties in the room would have been a more effective way to move these regulations into the 21st century, and we're seeing a lot of federal agencies start taking that next step. So I don't understand why the Federal Highway Administration wouldn't have done that as well.
Stephanie Rouse:I'm curious too, if the timing of Wes's book, if it had come out years ago when the conversation started on the update of the MUTCD, if it may have had greater impact, with more engineers understanding the lack of science behind a lot of these regulations.
Jennifer Hiatt:Yeah, maybe Because you make the point. The manual became more well known, but still by a very small amount of people in 2020. I feel like the conversation has advanced quite a bit more now, since Wes's book and a few others like Veronica Davis have come out.
Stephanie Rouse:The article proposes three areas of urgently needed reform the elimination of the 85th percentile rule, removing a proposal related to electric vehicles that would cause more harm to vulnerable road users, and the application of principles that reflect broader policy goals and that are informed by more than just vehicle-driven interests. Since this article was published, the manual has been released and while the 85th percentile is not gone, the approach to setting speed limits has significantly changed so that it's not a primary factor and other contextual factors such as land use, pedestrian activity, crashes and others now carry significant weight. This article, like the research from Killed by a Traffic Engineer, underpins the weak foundation that much of the traffic engineering manuals like the MUTCD the weak foundation that much of the traffic engineering manuals like the MUTCD are based on. For the 85th percentile, the FHWA is quoted as saying the original research between speed and safety, which purported that the safest travel speed is the 85th percentile speed, is dated research and may not be valid under scrutiny. Yet the 85th percentile somehow survived the update. Its emphasis was just downplayed a bit.
Jennifer Hiatt:And again, as this article states, the Federal Highway Administration should have eliminated the 85th percentile rule altogether, since the research was questioned at that point. This would have sent a clear message to government agencies who rely on it as a legal shield that they would no longer be acting in conformance with the manual as it stands. Now, even though the 85th percentile rule has been de-emphasized, it is still present in the manuals and I expect that government agencies will continue to rely on it as they have in the past.
Stephanie Rouse:Hard to change established engineers' patterns of operation right. The authors, like many transportation professionals focused on vulnerable road users, questioned the emphasis on electric vehicles as the solution we've all been waiting for. The draft MUTCD update included a new chapter. Part five related to traffic control device considerations for automated vehicles that the authors labeled premature, to the extent that it is intended to provide for fully automated vehicles. It also expresses an outdated, narrow view of transportation policy objectives. This section made it into the final document, but is only five pages of text that mostly spells out the operation and shortfalls of AVs and recommends consistency and signage and markings to help the cars figure out what's going on in the roadways. If adhered to, this means no more decorative crosswalks or context-sensitive design features.
Jennifer Hiatt:AV discussions always make me laugh a little, because we've heard for over 30 years that AVs are just two to five years away and they haven't materialized in any significant way. I especially laughed at the article's dismissive statement Six years after Elon Musk predicted a complete autonomy in approximately two years. The most successful completely automated vehicle is arguably a vacuum cleaner, the Roomba. As more and more research is conducted, it does not seem like AVs are going to be the holy grail solution at all, and as such, we should not be preemptively regulating for technology that might not ever fully materialize.
Stephanie Rouse:Yeah, and, as we pointed out in the last episode, there's plenty of people that will never adopt an autonomous vehicle, and so basing our traffic system around it is not a good path to go down. Agreed, even if all the signs and pavement markings were consistent and predictable. Avs have been proven to operate poorly in bad weather and are racially biased, not recognizing people with darker skin. Their safety benefits are questionable if they need such a perfect environment with no unique or inconsistent variables to function.
Jennifer Hiatt:Yeah, to your point and, as I definitely said in Killed by a Traffic Engineer episode, you will not be catching me in a Waymo anytime soon. I understand that I'm being a bit of a Luddite regarding this kind of technology, but you have to admit, luddites might have had a point. They might have been protecting their livelihoods. But honestly, in this case I think it's a.
Stephanie Rouse:There's already too many things going wrong with transportation, so why add a poorly functioning alternative into the mix type thing of road users, incorporating diverse expert and community opinions and facilitating local flexibility and innovation, especially in cities and communities disproportionately harmed by fast vehicular traffic? I feel like starting with that first lens fairness for all types of road users will lead to a dramatic reimagining of the manual and its recommendation. If we prioritize non-motorized traffic, we would stop requiring over 90 people to make a dangerous crossing before it's warranted for a signal to be put in. We would understand that a signal should be installed if it will increase safety for vulnerable road users.
Jennifer Hiatt:The way the authors put it, is in order to better represent public values and a variety of lawful and valuable users of the road beyond motor vehicle transportation. In seeking advice, the Federal Highway Administration should no more confine itself to the input of the traffic engineering profession than the Securities and Exchange Commission should limit itself to only the views of investment bankers. There's a wide variety of perspectives that need to be considered and at the moment, even with the comment period for rulemaking, the Federal Highway Administration isn't hearing or considering all sides of the conversation.
Stephanie Rouse:The authors recommend opening up the committee membership in charge of the MUTCD update to broaden experience and backgrounds beyond just transportation engineering professionals. This has merit in garnering outside perspectives from bike and pedestrian advocacy groups, environmental and public health experts. I'm also hopeful that, as mindsets are shifting and students are graduating with a different perspective and priorities, that the transportation professionals represented on the committee will bring a new, broader vision for the manual. While arguing the conflict between a uniform manual and the goal to provide local flexibility and innovation, the authors point out the uniformity has suffocated good designs at the local level, especially when rules require permission or an engineering study to deviate. It's obvious some standards need to be uniform across the spectrum, like red stop signs, but others, with installing a pedestrian signal when the land use patterns make sense, should be more localized decisions. A community with a population of 300,000 will have a harder time reaching warrants than a city with 1 million residents.
Jennifer Hiatt:Local context really does matter you know I never thought about that, but it's one of those things where, like, if you're waiting for a once in a million thing, but something happens 5 million times a day, that thing happens five times, it's only 300,000. You're not going to get there. For years I've never really thought about it like that. We hope you've enjoyed this conversation on rewriting our nation's deadly traffic manual. You can read the full article by Sarah Bronin and Gregory Schill by clicking the link in the show notes. Remember to subscribe to the show wherever you listen to podcasts, and please rate, review and share the show. Thank you.
