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/

Follow us on social media for more content related to each episode:

LinkedIn: https://www.linkedin.com/company/booked-on-planning/
Twitter: https://twitter.com/BookedPlanning
Facebook: https://www.facebook.com/bookedonplanning
Instagram: https://www.instagram.com/bookedonplanning/

Episode Transcript

Stephanie Rouse (00:12):
you're listening to the booked on
planning podcast, a project ofthe nebraska chapter of the
american planning association.
In each episode, we dive intohow cities function by talking
with authors on housing,transportation and everything in
between.
Join us as we get Booked onPlanning.

(00:40):
Welcome back, bookworms, toanother episode of Booked on
Planning.
We're continuing theconversation on traffic
engineering and narrowing into apart of our conversation that
we had with Wes Marshall ontraffic engineering manuals.
In 2021, sarah Bronnan andGregory Schill authored
Rewriting Our Nation's DeadlyTraffic Manual, which was
published in the Harvard LawReview.
The manual in question is themanual on uniform traffic

(01:01):
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'msure.
This 800-page document containsengineering guidance on
everything from the rule thatstop signs are to be read to how
to set speed limits with a veryquestionable method.
As you would have heard inlistening to Wes on our last

(01:24):
episode, this manual is verymuch vehicle-specific and
flow-first safety and mobility.

Jennifer Hiatt (01:30):
Last, I really appreciated that this article
was written from a legalperspective.
Sarah Bronin is a planner and alawyer who teaches at Cornell,
both in the School ofArchitecture, art and Planning
and the law school, and herco-author, gregory Schill,
teaches at the Iowa College ofLaw and the Iowa College of
Engineering.
So it's kind of an interestingperspective that I don't think
we've really heard or seen fromin the transportation world at

(01:53):
this point.
So over and over again, as wewere talking with Wes, I kept
thinking about howtransportation engineers keep
falling back on the MUTCD astheir legal backstop.
But there are plenty of otherlegal arguments to protect any
rational decision made by aprofessional in the course of
their professional duties.

Stephanie Rouse (02:08):
Yeah, very interesting connection there.
So the MUTCD dates back to 1935, when the Federal Highway
Administration adopted it as aguide for the fledgling field of
traffic engineering.
Barely into its first fewdecades of existence, it's now
in its 11th iteration, althoughadoption is pending in many
states.
This manual has incrediblepower in how we design our

(02:30):
cities and can result indangerous street designs and
hostile environments.
You may have never heard ofthis manual, but if you've ever
been told that your communitycan't install a pedestrian
crossing or paint a crosswalk afun design, this document is
what's prohibiting thatimprovement I always got so
confused why you couldn't do afancy crosswalk.

Jennifer Hiatt (02:48):
That's some of the most iconic art you've ever
seen, like the beatles walkingacross abbey lane and a really
cool crosswalk and whatever.
Like what is that?
And in many ways it makes a lotof sense to have a manual like
the mutcd.
The united states is a largecountry and it would cause
complete chaos if every statehad its own set of regulation.
It would be very dangerous ifgreen means go in Nebraska but

(03:09):
it means stop in Colorado.
So it makes sense to havesomething that's overarching,
and having the uniformity that'slaid out in the MUTCD is
important and if the manual hadstopped there it would be a
useful document.
But unfortunately it goessignificantly further, as you've
said and we talked about withWes, and it has massive reaching
impacts on the MUTCD, whilestill not a well-known document

(03:33):
to the masses, actually becamemore well-known.

Stephanie Rouse (03:35):
during its 2020 update to the 11th edition, the
Federal Highway Administrationproposed revisions that garnered
over 26,500 public comments.
Not only transportationengineers, but many varied
advocacy groups spoke outagainst the document, which had
minimal improvements, and would,as the authors put it, against
the document, which had minimalimprovements and would, as the

(03:56):
authors put it, quote perpetuatesome longstanding, arbitrary,
capricious or discredited rules,even as it introduced new ones
bearing the same defects.
It does this because it putsvehicle flow first, at the
expense of the safety ofpedestrians, bicyclists, transit
users and other vulnerable roadusers.

Jennifer Hiatt (04:10):
Arbitrary and capricious is the legal kiss of
death for cities, so maybe weshould be considering better
alternatives here.
This version of the manual,like many before it, states that
its purpose is to establishnational criteria for the use of
traffic control devices thatmeet the needs and expectancy of
road users on all streets,highways, bikeways and site
roadways open to public travel.

(04:33):
But then it turns around andprimarily considers road users
to be drivers of automobilesonly, and that bias shows up in
every part of the manual and isreally the most frustrating part
about it.

Stephanie Rouse (04:43):
One main section of the manual that
highlights this car bias is the85th percentile rule, which
justifies speed limits to createfree-flowing traffic.
The method looks at what speedis traveled at the 85th
percentile of drivers on aroadway, then sets the speed
accordingly, effectively makingthe speed what the driver
traveling faster than 85% ofother cars is going, instead of

(05:04):
designing a road for trafficspeeds that are safe for the
environment and then setting thespeed limit accordingly.
It also gives traffic engineersthe ability to raise the speed
limit, even if it would increasesafety concerns to legalize the
speeding of those 15% ofdrivers on a roadway.
It in effect delegates theinterpretation of the law to the
small group of driversviolating it the worst.

Jennifer Hiatt (05:25):
Yeah, it's such a perverse incentive.
Instead of rewarding the peoplewho go at or below the posted
speed limit, we are rewardingthose who willfully break a
posted law.
It's allowing the actions ofthe few to endanger the majority
, and it doesn't make sense.
Additionally, it already erasesthe needs or interests of
anyone that's actually not in acar.
When we should be encouragingmultimodal transportation

(05:47):
options, we are instead not eventaking them into consideration
in one of the most influentialguidelines on traffic speed out
there.

Stephanie Rouse (05:54):
The primary focus of the manual is to
increase traffic speeds andreduce traffic congestion, a
function realized during thepandemic, when remote work and
lockdowns were prominent.
What the article points out,though, is when this was finally
achieved.
It proved deadly, with 2020 asthe highest year-over-year
increase in roadway death rateson a per-mile travel basis in 96

(06:15):
years.
So you would think, seeing this, that the manual would need a
drastic shift in focus frommoving cars fast and freely to
slowing them down andprioritizing other modes of
travel.
Sadly, that's not what tookplace in the 11th edition update
.
Changes were made, but not thelarge-scale, impactful changes
that were needed.

Jennifer Hiatt (06:32):
It is unfortunate that the Federal
Highway Administration hasalready adopted the 11th version
.
I understand that they wentthrough the proper promulgation
of rules and procedures, but itseems to me that a larger
discussion with multiple partiesin the room would have been a
more effective way to move theseregulations into the 21st
century, and we're seeing a lotof federal agencies start taking
that next step.
So I don't understand why theFederal Highway Administration

(06:54):
wouldn't have done that as well.

Stephanie Rouse (06:56):
I'm curious too , if the timing of Wes's book,
if it had come out years agowhen the conversation started on
the update of the MUTCD, if itmay have had greater impact,
with more engineersunderstanding the lack of
science behind a lot of theseregulations.

Jennifer Hiatt (07:11):
Yeah, maybe Because you make the point.
The manual became more wellknown, but still by a very small
amount of people in 2020.
I feel like the conversationhas advanced quite a bit more
now, since Wes's book and a fewothers like Veronica Davis have
come out.

Stephanie Rouse (07:28):
The article proposes three areas of urgently
needed reform the eliminationof the 85th percentile rule,
removing a proposal related toelectric vehicles that would
cause more harm to vulnerableroad users, and the application
of principles that reflectbroader policy goals and that
are informed by more than justvehicle-driven interests.
Since this article waspublished, the manual has been

(07:49):
released and while the 85thpercentile is not gone, the
approach to setting speed limitshas significantly changed so
that it's not a primary factorand other contextual factors
such as land use, pedestrianactivity, crashes and others now
carry significant weight.
This article, like the researchfrom Killed by a Traffic
Engineer, underpins the weakfoundation that much of the

(08:10):
traffic engineering manuals likethe MUTCD the weak foundation
that much of the trafficengineering manuals like the
MUTCD are based on.
For the 85th percentile, theFHWA is quoted as saying the
original research between speedand safety, which purported that
the safest travel speed is the85th percentile speed, is dated
research and may not be validunder scrutiny.
Yet the 85th percentile somehowsurvived the update.
Its emphasis was justdownplayed a bit.

Jennifer Hiatt (08:32):
And again, as this article states, the Federal
Highway Administration shouldhave eliminated the 85th
percentile rule altogether,since the research was
questioned at that point.
This would have sent a clearmessage to government agencies
who rely on it as a legal shieldthat they would no longer be
acting in conformance with themanual as it stands.
Now, even though the 85thpercentile rule has been

(08:53):
de-emphasized, it is stillpresent in the manuals and I
expect that government agencieswill continue to rely on it as
they have in the past.

Stephanie Rouse (09:01):
Hard to change established engineers' patterns
of operation right.
The authors, like manytransportation professionals
focused on vulnerable road users, questioned the emphasis on
electric vehicles as thesolution we've all been waiting
for.
The draft MUTCD update includeda new chapter.
Part five related to trafficcontrol device considerations

(09:22):
for automated vehicles that theauthors labeled premature, to
the extent that it is intendedto provide for fully automated
vehicles.
It also expresses an outdated,narrow view of transportation
policy objectives.
This section made it into thefinal document, but is only five
pages of text that mostlyspells out the operation and
shortfalls of AVs and recommendsconsistency and signage and

(09:43):
markings to help the cars figureout what's going on in the
roadways.
If adhered to, this means nomore decorative crosswalks or
context-sensitive designfeatures.

Jennifer Hiatt (09:52):
AV discussions always make me laugh a little,
because we've heard for over 30years that AVs are just two to
five years away and they haven'tmaterialized in any significant
way.
I especially laughed at thearticle's dismissive statement
Six years after Elon Muskpredicted a complete autonomy in
approximately two years.
The most successful completelyautomated vehicle is arguably a

(10:14):
vacuum cleaner, the Roomba.
As more and more research isconducted, it does not seem like
AVs are going to be the holygrail solution at all, and as
such, we should not bepreemptively regulating for
technology that might not everfully materialize.

Stephanie Rouse (10:28):
Yeah, and, as we pointed out in the last
episode, there's plenty ofpeople that will never adopt an
autonomous vehicle, and sobasing our traffic system around
it is not a good path to godown.
Agreed, even if all the signsand pavement markings were
consistent and predictable.
Avs have been proven to operatepoorly in bad weather and are
racially biased, not recognizingpeople with darker skin.
Their safety benefits arequestionable if they need such a

(10:51):
perfect environment with nounique or inconsistent variables
to function.

Jennifer Hiatt (10:55):
Yeah, to your point and, as I definitely said
in Killed by a Traffic Engineerepisode, you will not be
catching me in a Waymo anytimesoon.
I understand that I'm being abit of a Luddite regarding this
kind of technology, but you haveto admit, luddites might have
had a point.
They might have been protectingtheir livelihoods.
But honestly, in this case Ithink it's a.

Stephanie Rouse (11:21):
There's already too many things going wrong
with transportation, so why adda poorly functioning alternative
into the mix type thing of roadusers, incorporating diverse
expert and community opinionsand facilitating local
flexibility and innovation,especially in cities and
communities disproportionatelyharmed by fast vehicular traffic
?
I feel like starting with thatfirst lens fairness for all

(11:41):
types of road users will lead toa dramatic reimagining of the
manual and its recommendation.
If we prioritize non-motorizedtraffic, we would stop requiring
over 90 people to make adangerous crossing before it's
warranted for a signal to be putin.
We would understand that asignal should be installed if it
will increase safety forvulnerable road users.

Jennifer Hiatt (11:59):
The way the authors put it, is in order to
better represent public valuesand a variety of lawful and
valuable users of the roadbeyond motor vehicle
transportation.
In seeking advice, the FederalHighway Administration should no
more confine itself to theinput of the traffic engineering
profession than the Securitiesand Exchange Commission should
limit itself to only the viewsof investment bankers.

(12:22):
There's a wide variety ofperspectives that need to be
considered and at the moment,even with the comment period for
rulemaking, the Federal HighwayAdministration isn't hearing or
considering all sides of theconversation.

Stephanie Rouse (12:34):
The authors recommend opening up the
committee membership in chargeof the MUTCD update to broaden
experience and backgroundsbeyond just transportation
engineering professionals.
This has merit in garneringoutside perspectives from bike
and pedestrian advocacy groups,environmental and public health
experts.
I'm also hopeful that, asmindsets are shifting and
students are graduating with adifferent perspective and

(12:55):
priorities, that thetransportation professionals
represented on the committeewill bring a new, broader vision
for the manual.
While arguing the conflictbetween a uniform manual and the
goal to provide localflexibility and innovation, the
authors point out the uniformityhas suffocated good designs at
the local level, especially whenrules require permission or an

(13:15):
engineering study to deviate.
It's obvious some standardsneed to be uniform across the
spectrum, like red stop signs,but others, with installing a
pedestrian signal when the landuse patterns make sense, should
be more localized decisions.
A community with a populationof 300,000 will have a harder
time reaching warrants than acity with 1 million residents.

Jennifer Hiatt (13:34):
Local context really does matter you know I
never thought about that, butit's one of those things where,
like, if you're waiting for aonce in a million thing, but
something happens 5 milliontimes a day, that thing happens
five times, it's only 300,000.
You're not going to get there.
For years I've never reallythought about it like that.
We hope you've enjoyed thisconversation on rewriting our

(13:55):
nation's deadly traffic manual.
You can read the full articleby Sarah Bronin and Gregory
Schill by clicking the link inthe show notes.
Remember to subscribe to theshow wherever you listen to
podcasts, and please rate,review and share the show.
Thank you.