CITY LIMITS Setting Safe Speed Limits on Urban Streets - Summer 2020 - National Association of City Transportation Officials
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CITY LIMITS Setting Safe Speed Limits on Urban Streets Summer 2020
NACTO City Limits City Limits NACTO
Acknowledgements
NACTO MEMBER WORKING GROUP Lily Reynolds, Deputy Director of Complete ABOUT NACTO NACTO PROJECT TEAM
Streets, Philadelphia oTIS
Christopher Cairns, City Transportation Gustave Scheerbaum, P.E., Director NACTO’s mission is to build cities as Corinne Kisner, Executive Director
Engineer, City of Orlando of Strategic Initiatives, Transportation, places for people, with safe, sustainable,
Kate Fillin-Yeh, Director of Strategy
Philadelphia oTIS accessible, and equitable transportation
Najah Casimir, Communications Manager,
choices that support a strong economy and Zabe Bent, Director of Design
City of Cambridge Traffic, Parking & Brad Topol, Interim Vision Zero Coordinator, vibrant quality of life. We do this by:
Transportation Seattle Department of Transportation Jenny O’Connell, Program Manager
• Communicating a bold vision for 21st
Charlotte Castle, Deputy Chief of Staff, Liliana Quintero, Senior Transportation Matthew Roe, Technical Lead
century urban mobility and building
Managing Directors Office, Philadelphia Engineer, City of Vancouver strong leadership capacity among city Alex Engel, Communications Manager
oTIS
transportation officials.
Kelley Yemen, Director of Complete Streets, Sindhu Bharadwaj, Policy Associate
Dongho Chang, City Traffic Engineer, Philadelphia Office of Transportation, • Empowering a coalition of cities to lead
Seattle Department of Transportation Infrastructure, and Sustainability Celine Schmidt, Design Associate
the way on transportation policy at the
Ethan Fawley, Vision Zero Program local, state, and national levels.
Coordinator, City of Minneapolis Public
• Raising the state of the practice for
Works EXTERNAL REVIEWERS street design that prioritizes people
Tim Frémaux, Senior Transportation walking, biking, and taking transit.
Engineer, Valley and Western District Sarah Abel, Technical Programs Manager,
Operations, Los Angeles Department of Institute of Transportation Engineers
Transportation Jessica Cicchino, Vice President, Research, NACTO EXECUTIVE BOARD
Lacey Hirtle, Senior Traffic Safety Engineer, IIHS
City of Vancouver Charlotte Claybrooke, Active Transportation Janette Sadik-Khan, NACTO Chair
Program Manager, Washington State Principal, Bloomberg Associates
Matt Kelly, Vision Zero Specialist, Porltand
Bureau of Transportation Department of Transportation
Robin Hutcheson, NACTO President
Julia Kite-Laidlaw, Director of Strategic Jackie DeWolfe, Director of Sustainable Director, Minneapolis Department
Initiatives, New York City Department of Mobility, Massachusetts Department of of Public Works
Transportation Transportation
Eulois Cleckley, NACTO Vice President
James Le, Senior Civil Engineer, Seattle Wen Hu, Senior Research Transportation
Executive Director, Denver Department of
Department of Transportation Engineer, IIHS
Transportation & Infrastructure
Brooke McKenna, Assistant Director for Beth Osborne, Director, Transportation for
Street Management, City of Cambridge America Michael Carroll, NACTO Secretary
Traffic, Parking & Transportation Deputy Managing Director, Office of
Leah Shahum, Executive Director, Vision
Transportation and Infrastructure Systems,
Richard Montanez, P.E., Deputy Zero Network
City of Philadelphia
Commissioner for Transportation, Eric Sundquist, Director, State Smart
Philadelphia oTIS Transportation Initiative, University of Robert Spillar, NACTO Treasurer
Ryan Noles, Senior Transportation Planner, Wisconsin Director of Transportation, City of Austin
City of Boulder Veronica Vanterpool, Principal, V Squared
Joseph Barr, NACTO Affiliate Member
Ryan Reeves, Vision Zero Program Lead, Strategies
Representative; Director, Traffic, Parking, &
Sustainable Streets Division, San Francisco Transportation, City of Cambridge
Municipal Transportation Agency
2 3
NACTO City Limits City Limits NACTO
Table of Contents
Key Terms & Definitions Acknowledgements 2
Key Terms & Definitions 4
Absolute Speed Law: A legal environment in which drivers must never drive faster
than the posted speed limit, regardless of what they deem safe for conditions. Speed Limits Conversions 4
Executive Summary 6
Basic Speed Law: A legal environment in which drivers must never drive faster
than is safe for present conditions, regardless of the posted speed limit. About This Document 7
Design Speed: The speed on which the geometry or physical elements of the
roadway is based.
1 The Need 8
Operating Speed: The speed at which vehicles are traveling along a roadway.
Rethinking Safety 11
Posted Speed Limit: The maximum lawful speed as displayed on a regulatory sign. Speed Kills 14
Statutory Speed Limit: The speed limit established under law, which applies in How Speed Kills 15
the absence of a posted speed limit. Designed to Fail: The problem with percentile-based speed limits 18
Target Speed: The highest speed that designers intend drivers to go on a specific Speed Limit Changes Have Big Impacts 22
street or road.
2 The Tools 26
Tools to Change Speed Limits 28
Speed Limits Conversions Authority to Change Speed Limits
Combining Tools
29
31
Case Studies in Lowering Speed Limits 35
10 15 25 40
KPH
MPH KPH MPH
3 The Right Speed Limits 40
Recommended Speed Limits 42
15 25 30 50
KPH
MPH KPH MPH Default Speed Limits 44
20 30
KPH
35 60 Defining Slow Zones 52
MPH MPH KPH
Corridor Speed Limits / Conducting Safe Speed Surveys 56
4 Checklists 90
4 5
NACTO City Limits City Limits NACTO
Executive Summary About This Document
We cannot reduce traffic fatalities on US city setting speed limits in urban areas. In many In 2018, NACTO convened a working group with commercial, residential, or retail uses
streets without reducing speeds. places, cities have turned to increased police of major US cities to develop new robust along one or both sides. This guidance is
enforcement to compensate for restrictive guidance for setting speed limits on urban also applicable on streets like these in non-
More than 35,000 people die in traffic crashes
engineering and speed limit setting policies, streets that could provide an alternative to the urban areas. This guidance is not applicable
on US roads each year, and millions more are
a practice that is not proven to reduce serious highway-focused federal recommendations. on limited access streets, even within cities,
seriously and often permanently injured. The
injuries or fatalities, and often increases risk Over the course of the following 18 months, or on rural or very low density streets with
United States has the highest fatality rate in
for Black, Indigenous, and people of color transportation staff from 19 cities helped to limited multimodal use.
the industrialized world; double the rate in
(BIPOC) on city streets. write and review the guidance and provided
Canada and quadruple that in Europe. While Finally, the speed limit setting guidance
technical expertise based on their experience
traffic fatalities may seem like an intractable This document, City Limits, is intended to contained in City Limits is only one piece of
developing speed management strategies
issue, city governments have the power to provide city practitioners with guidance on a larger, essential discussion around how
and programs and implementing lower speed
reduce the frequency and severity of traffic how to strategically set speed limits on urban to make streets truly safe for everyone.
limits in their own cities.
crashes by reducing motor vehicle speeds. streets, using a Safe Systems approach, Speeding vehicles pose a significant, specific,
to reduce traffic fatalities and injuries. The resulting guidance, City Limits, provides and deadly threat, but comprehensive safety
Addressing speed is fundamental to making
Recognizing that city authority to set speed cities with clear technical and policy guidance on city streets and public spaces involves
streets safer. Vehicle speed increases both
limits varies by jurisdiction, City Limits offers on setting safe speed limits on city streets. All a more holistic consideration of risks—
the likelihood of a crash, as well as the severity
three tools for setting speed limits on urban of NACTO’s Member Agencies (81 members from accessibility to gender identity-based
of the crash, as it diminishes drivers’ ability
streets: at the time of final review) have approved harassment to racial violence. In particular,
to recognize and avoid potential conflicts. In
this guidance. The technical guidance and speed enforcement as currently practiced
addition, on streets with higher speeds and
recommended maximum speed limits in this poses additional, disproportionate health
higher speed limits, traffic engineers have Setting Default Speed Limits on many document are based on input from NACTO and safety risks especially to Black and
fewer design options to increase safety. streets at once. member agencies, academic studies about Latinx people. Manual police enforcement is
In cities, transportation agencies have long speeds that minimize conflict and risk, and a less effective way to manage speeds down
understood that motor vehicle speed plays a best practices in cities across the world. over time than street design and engineering
Designating Slow Zones in sensitive
key role in fatal and serious crashes, and have changes, and can create dangerous physical
areas. Unlike existing national guidance, City Limits
sought to reduce speeds through design and and mental health impacts for Black,
focuses on urban streets, which pose the most
regulation in order to save lives. But speed Indigenous, and people of color (BIPOC), as
challenging scenarios for determining speed
limit reductions have remained out of bounds well as other marginalized road users. This
Setting Corridor Speed Limits on high limits and are where the majority of pedestrian
for many city transportation agencies because resource touches on speed enforcement, but
priority major streets using a Safe Speed and cyclist fatalities occur. In this document,
authority over speed limits, even on city it is not the focus of this guidance. City Limits
Study. urban streets refer to most of the categories
streets, is often held at the state level, and is addresses speed limit setting policy which,
of streets found in North American cities,
commonly tethered to the practice of using the City Limits maps a new path for US cities, paired with street design, is the best tool for
including local, primarily residential streets,
existing speeds on a street to determine what codifying speed limit setting best practices reducing the health and safety risks posed by
mixed use corridors, transit corridors, high
the speed limit should be. This flawed model that have been tested and documented in vehicular speeds.
density downtown streets, and urban arterials
uses the current behavior of individuals to cities across North America. Cities can create
determine the speed limit, instead of allowing better and safer outcomes for all by adopting
engineers and planners to set the limit at these speed limit setting practices as part of
the speed that will create the best, safest their traffic fatality reduction or Vision Zero
conditions for all road users. The result is programs. By managing speeds, cities can
higher speeds and speed limits over time. save lives.
Practitioners often find themselves with
limited recourse to address these challenges
because they lack an alternative method for
6 7
NACTO Setting Safe Speed Limits NACTO Setting Safe Speed Limits
NEW YORK CITY
Photo: City of New York
1
The
Need
The Need NACTO City Limits City Limits NACTO The Need
SEATTLE
Rethinking Safety
In 2018 alone, drivers killed 36,560 people on US streets are becoming especially
US roads and seriously injured millions more.1,2 dangerous for people walking and biking.
These tragedies are the result of a failed Between 2009 and 2018, pedestrian deaths
approach to traffic safety that prioritizes from traffic crashes in the US grew by 46%,
speed and convenience over human lives. reaching a nearly 3-decade high of 7,354
people killed by vehicles in 2018 alone.4,5
Experience from other industrialized countries
This rate means that people walking and
shows that fewer traffic deaths and safer roads
biking are an increasingly large percentage
are possible. Rather than focusing on individual
of all fatalities on the road. For the past
behavior, these countries focus on changing
five years, pedestrians and cyclists have
the policies and engineering decisions that
accounted for almost 20% of all road
create unsafe conditions. This technique, also
fatalities, despite making up only 11% of
known as a Safe Systems approach, is the
road users.6,7 And this number is on the rise.
guiding philosophy behind the safer streets in
From 2008 to 2018, cyclist and pedestrian
European Union and Scandinavian countries,
fatalities increased by 38% versus a 12%
which have, on average, a per capita traffic
decline for vehicle occupants.8
fatality rate that is half and a third, respectively,
of that in the United States.3 Compounding these statistics, reliance on
increased police enforcement to address
dangerous driving in the name of “safety”
Safety for all road users must be set has contributed to the disproportionate
number of Black people stopped, injured,
as the foremost goal, and all decisions
and killed by the police.9
must be made based on how well they
advance work toward zero deaths.
PEDESTRIAN FATALITIES HAVE BEEN STEADILY RISING SINCE 2009
7,000
6,000
Pedestrians killed
5,000
4,000
2000 2005 2010 2015
Photo: City of Seattle
10 11
The Need NACTO City Limits City Limits NACTO The Need
In cities, where the vast majority of pedestrians infrastructure to support that speed. PHILADELPHIA
and cyclists are killed, transportation agencies Instead of being forced upward over time,
have long understood that motor vehicle speeds, and fatalities, would go down as
speed plays a key role in fatal and serious they have in the countries that use such
crashes, and have sought to reduce speeds approaches.
and save lives. But speed limit reductions
To reduce traffic deaths and severe injuries
have remained out of bounds for many city
in the US, transportation policymakers must
transportation agencies because authority
change their approach. Safety for all road
over speed limits, even on city streets, is
users must be set as the foremost goal, and
often held at the state level, and is commonly
all decisions—about speed, infrastructure,
tethered to the practice of using the existing
allocation of parking and other curbside
speeds on a street to determine what the
uses, enforcement, and maintenance—
speed limit should be. This method results in
must be made based on how well they
higher speeds and speed limits over time.10
advance work toward zero deaths. By taking
If the US approached speed limit setting a holistic, Safe Systems approach to street
using a Safe Systems approach, engineers design, cities can reduce speeds, build safer Photo: Charles Mostoller
would determine the speed that is safest streets, and save lives.
for all people using the street and then build
RACISM EXACERBATES THE DANGERS OF SPEEDING
Structural and individual racism exacerbate to a White pedestrian actively crossing in the
TRAFFIC FATALITIES ARE DECLINING IN MOST OTHER INDUSTRIALIZED the dangers posed by speed. In their 2019 crosswalk only about 3% of the time versus
COUNTRIES, BUT RISING IN THE US11 Dangerous by Design report, Smart Growth 21% of the time for a Black pedestrian.16
America finds that Black, Indigenous, and
25 Finally, relying on traffic stops as a primary
Latinx people are more likely than White people
method for managing speeds can hinder
to be struck and killed by a driver.12 Street
larger efforts to improve overall community
conditions are often worse in low-income
safety on streets and deepen the role
20 neighborhoods and those where people of
of transportation in structural poverty,
color are the majority. Historically, in many
where enforcement targets low-income
Deaths per 100,000
cities, redlining justified underinvestment in
communities. According to the Department
15 public services for communities of color, while
of Justice, about half of all interactions with
Russia past and current highway siting decisions,
police begin with a traffic stop or crash.17
United suburban-focused traffic engineering
But data shows that when enforcing traffic
States practices, and disinvestment in urban cores,
10 laws, police disproportionately stop Black
result in substandard, dangerous streets in
Sweden Spain people and other people of color, sometimes
predominantly low-income, immigrant, and
UK Italy with fatal consequences.18 By focusing only
BIPOC communities.13
5 Norway Canada on reducing traffic fatalities at the cost of
Mexico Japan
Recent studies from Portland State University increasing risk of fatalities due to police
Austria Australia
Netherlands
and the University of Nevada, have found violence and undue stress, transportation
0 racial bias in how quickly or frequently drivers planners, engineers, and practitioners
‘95 ‘97 ‘99 ‘01 ‘03 ‘05 ‘07 ‘09 ‘11 ‘13 ‘15 ‘17 yield to pedestrians in crosswalks.14,15 In erode their credibility with the communities
particular, in higher-income neighborhoods, they serve and undercut the momentum for
researchers found that drivers failed to yield safer streets as a whole.
12 13
The Need NACTO City Limits City Limits NACTO The Need
Speed Kills How Speed Kills
Speed is a central factor in traffic deaths. The Higher speeds are more likely to result in crashes
National Highway Traffic Safety Administration because the amount of time a driver has to hit the
1 2
reports that speed was a factor in a quarter of brakes or swerve decreases at higher speeds,
all fatal crashes in 2018.19 As speed limits and while vehicle braking distances increase.23,24 A
speeds increase, so do fatalities. Researchers driver going 40 mph travels twice as far as a driver
from the Insurance Institute for Highway traveling at 25 mph before coming to a complete Crashes at higher speeds Drivers traveling at
Safety (IIHS) found that a 5 mph increase in the stop.25,26,27 Research also shows that drivers have are more forceful and thus higher speeds have a
maximum speed limit was associated with an less peripheral awareness at higher speeds and
more likely to be fatal narrower field of vision
8% increase in the fatality rate on interstates are less likely to see or predict potential conflicts
and freeways, and a 3% increase in fatalities such as people crossing the street or children
on other roads.20 playing.28 Meanwhile, crashes are more likely to
be fatal at higher speeds because these crashes
25
Vehicle speed at the time of impact is directly MPH
are more forceful.
correlated to whether a person will live or die. 100 O
45
Force
A person hit by a car traveling at 35 miles per As a result, evidence shows that small
65 O MPH
hour is five times more likely to die than a reductions in speed result in large safety gains.29
person hit by a car traveling at 20 miles per The Highway Safety Manual reports that a 1 mph
hour.21 The risk of death at every speed is reduction in operating speeds can result in a 17%
higher for older pedestrians and pedestrians decrease in fatal crashes.30 A separate study
Speed
hit by trucks and other large vehicles.22 found that a 10% reduction in the average speed
resulted in 19% fewer injury crashes, 27% fewer
High speed crashes are more likely to occur
severe crashes, and 34% fewer fatal crashes.31
than crashes at lower speeds and, when they
do occur, they’re more likely to be deadly.
THE LIKELIHOOD OF FATALITY INCREASES EXPONENTIALLY WITH VEHICLE SPEED32 3 4
Drivers traveling at higher Vehicles traveling at
100% Hit at 50 mph,
speeds travel further higher speeds have
Common Speed 75% of people
Limits on Urban will die before they can react longer braking distances
Arterials
75%
Likelihood
50%
20 63 ft
of Death MPH
Hit at 32 mph,
25% of people
Hit at 23 mph,
will die 30 119 ft
25% 10% of people MPH
will die
0%
40 164 ft
MPH
15 25 35 45 55
MPH MPH MPH MPH MPH
thinking braking
Impact Speed
14 15
The Need NACTO City Limits City Limits NACTO The Need
PITTSBURGH
High speed driving is particularly deadly Urban arterials are typically signed for 35-
where different types of road users share 45 miles per hour or higher, and are designed
space and must interact frequently. In the to support high speeds by featuring wide,
US, fatal crashes are disproportionately highway-width lanes, sweeping turn radii,
clustered on a small group of high speed, and few places to stop for people to cross.
auto-oriented streets, known as urban In many cities, urban arterials often lack
arterials. Between 2014 and 2018, urban basic protections for people outside of cars,
arterials accounted for 29% of all fatal such as sidewalks, even when bus stops
crashes in the US and half (49%) of all fatal are present or when the adjacent retail/
crashes involving people biking or walking, commercial land uses encourage people to Photo: City of Pittsburgh
despite making up only 6% of US roadways.33 go there.
TWO TAKES ON SAFETY-FIRST SYSTEMS APPROACHES
INCREASING VEHICLE SIZE COMPOUNDS THE DANGERS OF SPEED Vision Zero saves lives US Aviation makes an impact
In the US, the trend toward larger and they have a taller frame, which Shifting an entire system from unsafe to safe By nearly every measure, commercial
vehicles compounds the problems posed increases the likelihood that, if struck, a is not just an aspiration. Many US cities have aviation is the safest transportation mode
by excessive speeds. In 2017, 43% of person (especially a child) will be pulled adopted safety-first programs, to varying in the United States. There were 3 fatal
pedestrian and cyclist fatalities involved under the vehicle rather than pushed degrees of success. Vision Zero, Injury crashes between 2010 and 2017, compared
an SUV, pickup truck or other light onto the hood. Minimization, and Safe Systems programs to 17 fatal crashes in 1960 alone.38 These
truck.34 In 2015, the National Highway affirm safety as the top transportation priority safety gains are the result of systemwide,
The US trend toward larger, more and the most effective way to eliminate traffic interdisciplinary approaches to managing
Traffic Safety Administration found that
dangerous vehicles is only growing. fatalities. Establishing a safety-first program: risk on the part of regulators and the
pedestrians are two to three times more
SUVs and pickup trucks outsold sedans commercial aviation industry.
likely to die when hit by an SUV or pickup > Signals a commitment to zero traffic
more than three-to-one in 2019, and
than by a passenger car.35 deaths on city streets In 1997, the White House Commission on
companies like Ford and Fiat Chrysler
> Asserts a belief that such a goal Aviation Safety & Security and the National
Larger vehicles are more lethal than have announced that they will stop
is attainable Civil Aviation Review Commission released
smaller ones for two main reasons: they producing the vast majority of their
> Accepts the role of officials, reports calling for the Federal Aviation
are heavier, which increases the force of sedans and compact cars.36
engineers, and planners in Administration (FAA) and airlines to work
the impact when combined with speed;
making streets safer together to reduce fatal accidents.39 In
Safety-first programs recognize that although response, the FAA partnered with airlines to
CLEVELAND
human error is inevitable, fatalities and severe form the Commercial Aviation Safety Team
injuries are preventable through street design (CAST), which uses incident data to discern
and management choices. Successful safety safety priorities, deploys interdisciplinary
programs systematically change the way teams to determine underlying crash
streets operate to keep users safe, even when causes, and applies interventions based on
individuals make mistakes. their findings.
Sweden has created one of the most In 2009, Continental Flight 3407 crashed,
successful Vision Zero programs to date. In killing all 49 people on board and one
1997, when Sweden adopted its Vision Zero person on the ground. Pilot error and fatigue
program, there were more than 7 traffic were the listed causes. By 2013, the FAA
deaths per 100,000 people. Today, despite dramatically increased both training and
more than 20 years of growth in traffic rest requirements for pilots.40 Humans in
Photo: Angie Schmitt, @schmangee volume, this number has dropped to 3 people the commercial aviation industry make
on Twitter, Cleveland, OH per 100,000.37 mistakes. However, a systems approach to
safety has resulted in substantive safety
gains across the entire industry.
16 17
The Need NACTO City Limits City Limits NACTO The Need
Designed to Fail
THE PROBLEM WITH PERCENTILE-BASED SPEED LIMITS
Current speed limit setting practice in the US Two issues are at play. First, percentile-based Posting higher speed limits does not increase wider range of speeds. This can increase
uses a percentile-based method, typically set models are designed to respond to extremes. compliance with the law. Even when higher the likelihood of crashes because people
at the 85th percentile, to determine speeds. When enough people drive faster than the speed limit signs are posted, some number are traveling at increasingly different
Traffic engineers record how fast vehicles are set percentile, the model rewards them by of people will still choose to drive 5-15 mph speeds, and increases the likelihood that
traveling on a road, determine the speed that instructing traffic engineers to increase the faster than the posted limit. These “high- crashes will be fatal because they occur at
85 percent of drivers are traveling at or below, posted speed. end” speeders travel even faster as speed higher speeds.
then set the new speed limit by rounding from limits rise and typically spread out over a
Second, people decide how fast to drive based
that speed to the nearest 5 mph increment.
on both the street’s design and cues such as
Traffic engineers who use the 85th percentile
the posted speed and other drivers’ speeds.
method are instructed to raise the speed limit USING PERCENTILES TO DETERMINE SPEED LIMITS
Researchers originally recommended using = 5 vehicles (out of 100)
when more than 15% of drivers are driving RESULTS IN INCREASED SPEEDS OVER TIME recorded in speed study
the 85th percentile approach to determine
faster than posted signs. This method forces
posted speeds, assuming that drivers always
engineers to adjust speed limits to match
travel at reasonable speeds.41 But a growing
observed driver behavior instead of bringing
body of research shows that drivers base their
driver behavior in line with safety goals and the
decisions at least partially on the posted speed
law. When it comes to safety, this method is
limit.42,43 When they see higher posted limits,
designed to fail. 50
and see the resulting increased speed of their
MPH
Percentile-based speed limit setting methods peers, they drive faster too, which results in an
fail at keeping people safe because they set a increased speed of the street overall.44
85th
permanently moving target based on current
percentile
human behavior, not safety. speed
45
MPH
People choose their speed
depending on posted speed
85th
Traveling Speed
signs and keeping up with
percentile
other drivers (aka “going the speed
Based on observed DRIVERS SPEED 40
speed of traffic”). MPH
traffic speeds,
cities set new,
higher posted
85th
speed limits. percentile
35
MPH
speed
NEW POSTED SPEED SPEED STUDY
Cities measure
the speed of 30
MPH
40 traffic and
MPH identify the 50th
or 85th
percentile speed.
1st Speed Study 2nd Speed Study 3rd Speed Study
18 19The Need NACTO City Limits City Limits NACTO The Need
RURAL CONNECTICUT
In cities and other urban contexts, time to 45 mph. While other additional factors
percentile-based speed limit setting may also have played a role in speeds inching h t t p s : //p o r t a l .
methods are particularly dangerous because up over time, absent any design or land use c t . g o v /_ D
ht tps://w w w.f lickr.com/photos/sdot O T /84729324 37/
photos/4
they are based on outdated research that changes, the increase suggests that the 85th General/History/
in/photolist-2gRos3r-JKvGUx-FCFnYi-X6Q7rc-XeTjss-qNCj7y-
22Aq162-X6Q7oX-24fbPXm-2gzqxCf-Fs1iyb-2heaNTc-F9RfHF-
is inapplicable in urban settings.45 The percentile operating speed can shift over time Historical-
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1940s-era research supporting the 85th in accordance with the posted speed limit. Merritt-Parkway-
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percentile relied on self-reported crash Notably, this time period in LA corresponded to Images
NKmLoM-2bNarFf-eQ1xmX-2cgMt1f-2a4Laue-Pq3c1o-PYQBwZ-
data and was conducted on two-lane rural a 92 percent increase in pedestrian fatalities.48 28mz4Eo-Huyy81
highways, devoid of multimodal activity.46
The most commonly cited alternative for
But these historic roads are a far cry from the
the 85th percentile is USLIMITS2, an online
vibrant streets and arterials that typify city Photo: State of Connecticut DOT
tool developed by the Federal Highway
streets today. In particular, rural roads and
Administration that incorporates other factors The research supporting the use of the 85th percentile method was conducted on rural,
highways lack the type or volume of conflicts
when determining speed limits. USLIMITS2 is two-lane highways.
found in cities, such as people crossing the
a step forward in that it allows practitioners to
street, and people biking, walking, or rolling at
also consider the street’s most exposed users.
a variety of speeds. They also lack driveways,
However, it still relies on the 85th or, more
loading, parking, and double-parking.
commonly in urban areas, the 50th percentile AUSTIN
Los Angeles’ experience with Zelzah Avenue operating speed, which is often still much
provides a telling example of the dangers higher than is safe. Relying on a percentile-
of percentile-based speed limit setting. based system focused on current driver
In 2009, Los Angeles conducted a traffic behavior, rather than a defined safety target
speed study and raised the speed limit on to set speed limits, significantly limits cities’
Zelzah Avenue from 35 mph to 40 mph.47 In ability to reduce traffic deaths.
2018, the city again studied existing traffic
speeds, and again raised the speed limit, this
Relying on a percentile-based system focused on
Photo: Capital Metro
current driver behavior, rather than a defined safety
target to set speed limits, significantly limits cities’ But streets in cities are full of people walking, biking, using transit, and driving all in close
ability to reduce traffic deaths. proximity. The 85th percentile method for setting speed limits has never accounted for
these types of conditions.
20 21The Need NACTO City Limits City Limits NACTO The Need
Speed Limit Changes SPEED LIMIT REDUCTIONS ALONE CAN REDUCE SPEEDS AND CRASHES
Have Big Impacts CASE STUDY CASE STUDY
TORONTO SEATTLE
Rethinking how urban speed limits are set Reducing the posted speed limit unlocks a
improves safety for people in a number of variety of engineering and design tools that can
ways. Even changing the posted speed limit further increase safety on a street and support Seattle DOT replaced existing 30 mph
In Toronto, Researchers at The Hospital
sign creates safety benefits and allows other policy goals. Typically, the posted speed signs spaced 1 mile apart with 25 mph
for Sick Children found that on streets
cities to provide more and better safety of a street dictates what infrastructure and signs placed 1/4 mile apart on a 1.3 mile
where speed limits were lowered from
treatments, and improve overall quality of safety elements can be included in the final stretch of Greenwood Ave. North /
40 kph to 30 kph, there was a 28%
life. street design. For example, if the posted speed Phinney Ave. North, and saw reductions
decrease in the number of collisions
is 30 mph, a wider curb radius will be required in 85th and 50th percentile speeds, as
A growing body of research shows that speed between pedestrians and motor
than if the posted speed is 25 mph. The wider well as all crashes and injury crashes.
limit changes alone can lead to measurable vehicles and a 67% decline in the
curb radius increases exposure and risk for During this time, the city did not
declines in speeds and crashes, even absent number of fatal and serious injuries on
people walking and biking.51 All too often, increase marketing or enforcement, nor
enforcement or engineering changes. For streets with speed limit reductions.
essential pieces of safety infrastructure— did they make any engineering changes.
example, a 2017 Insurance Institute for
raised crossings, bike lanes, corner bulb-
Highway Safety study in Boston found that
outs—are ironically ineligible for inclusion in a
just reducing the citywide speed limit to 25
street redesign because drivers are currently
mph from 30 mph reduced speeding overall
going too fast. In effect, the street is too
and dramatically decreased the instances of
high-end speeding (vehicles traveling faster
dangerous to build safety infrastructure. 40 30 30 25
KPH KPH MPH MPH
than 35 mph).49 Reducing posted speeds creates opportunities
for safer street designs that also support other
Similarly, in Canada, researchers at The Decreases in... Decreases in...
policy goals. Similar to curb radii decisions,
Hospital for Sick Children found measurable
often infrastructure that supports transit
safety gains after Toronto lowered speed
and other sustainable modes like biking and PEDESTRIAN-VEHICLE FATAL & SERIOUS 85TH PERCENTILE
limits from 40 kilometers per hour (~25 mph) COLLISIONS INJURIES SPEED ALL CRASHES
walking, cannot be included in a design if the
to 30 kilometers per hour (~20 mph) on a
posted speed is too high. City policies around
number of local streets.50 34 MPH 30
safety, economic sustainability, equity, carbon
Recent efforts in Seattle underscore emissions reductions, and increased transit,
31 MPH
this pattern. There, the Department of bike, and walk mode share are interconnected.
Transportation saw significant speed and Rethinking speed limits unlocks the door
crash reductions when they lowered the for better design and safer streets, which
21
speed limit to 25 mph and increased the increases opportunities for all.
density of speed limit signs on select streets. -28%
All too often, essential pieces of safety infrastructure—
raised crossings, bike lanes, corner bulb-outs—are
ironically ineligible for inclusion in a street redesign -67%
before after before after
because drivers are currently going too fast.
22 23The Need NACTO City Limits City Limits NACTO The Need
Section 1 Endnotes
1. National Highway Traffic Safety Administration. 15. Coughenour, Courtney, et al. (January 29. Poole, B., Johnson, S., and Thomas, L. 41. Federal Highway Administration (2012). Methods and
Fatality Analysis and Reporting System. Retrieved 2017). Examining racial bias as a (December 2017). An Overview of Automated Practices for Setting Speed Limits: an Informational
from: https://www.nhtsa.gov/es/research-data/ potential factor in pedestrian crashes. Enforcement Systems and Their Potential for Report. Retrieved from: https://safety.fhwa.dot.gov/
fatality-analysis-reporting-system-fars. Accident Analysis & Prevention, 98, pp. Improving Pedestrian and Bicyclist Safety. speedmgt/ref_mats/fhwasa12004.
96-100. Retrieved from: https://www. Pedestrian and Bicycle Information Center.
2. National Highway Traffic Safety Administration. sciencedirect.com/science/article/abs/pii/ Chapel Hill, NC. Retrieved from: http://www. 42. Hu, W. and J. Cicchino (2019). Lowering the speed
Table 54: Persons Killed or Injured, by Person Type S000145751630361X?via%3Dihub#abst0010. pedbikeinfo.org/cms/downloads/WhitePaper_ limit from 30 to 25 mph in Boston: effects on vehicle
and Injury Severity, 2017. Retrieved from: https:// AutomatedSafetyEnforcement_PBIC.pdf. speeds. Insurance Institute for Highway Safety.
cdan.nhtsa.gov/SASStoredProcess/guest. 16. Ibid. Retrieved from: https://www.iihs.org/topics/
30. American Association of State Highway and bibliography/ref/2168.
3. World Health Organization. Global Health 17. US Department of Justice (October 2018). Transportation Officials (2010). Highway
Observatory data repository: Road traffic deaths. Contacts Between Police and the Public, 2015. Safety Manual. Retrieved from: http://www. 43. Fridman, L., Ling, R., Rothman, L. et al. (2020). Effect
Retrieved from http://apps.who.int/gho/data/node. Retrieved from: https://www.bjs.gov/content/ highwaysafetymanual.org/. of reducing the posted speed limit to 30 km per hour
main.A997. pub/pdf/cpp15.pdf. on pedestrian motor vehicle collisions in Toronto,
31. Nilsson, G. (2004). Traffic safety dimensions and Canada - a quasi experimental, pre-post study. BMC
4. National Highway Traffic Safety Administration 18. Stanford Open Policing Project. Retrieved from: the Power Model to describe the effect of speed on Public Health 20, 56. Retrieved from: https://doi.
(October 2019). 2018 Fatal Motor Vehicle Crashes: https://openpolicing.stanford.edu/findings/. safety. Traffic Engineering. Retrieved from: https:// org/10.1186/s12889-019-8139-5.
Overview. Retrieved from: https://crashstats.nhtsa. lup.lub.lu.se/search/ws/files/4394446/1693353.
dot.gov/Api/ Public/ ViewPublication/812826. 19. National Safety Council. Motor Vehicle Safety 44. National Traffic Safety Board (25 July, 2017).
pdf.
Issues: Speeding. Retrieved from: https:// Reducing Speeding-Related Crashes Involving
5. National Highway Traffic Safety Administration. injuryfacts.nsc.org/motor-vehicle/motorvehicle- 32. Tefft, B.C. (2011). Impact Speed and a Pedestrian’s Passenger Vehicles. Retrieved from: https://www.
Fatality Analysis and Reporting System. Retrieved safety-issues/speeding/. Risk of Severe Injury or Death. AAA Foundation ntsb.gov/safety/safety-studies/Documents/SS1701.
from: https:// www.nhtsa.gov/es/research-data/ for Traffic Safety. Retrieved from: https:// pdf.
fatalityanalysis-reporting-system-fars. 20. Farmer, Charles (April 2019). The effects of
aaafoundation.org/impact-speed-pedestrians-
higher speed limits on traffic fatalities in the 45. Taylor, Brian D. and Yu Hong Hwang (30 June, 2020).
risk-severe-injury-death/.
6. Ibid. United States, 1993–2017. Retrieved from: Eighty-Five Percent Solution: Historical Look at
https://www.iihs.org/api/datastoredocument/ 33. National Highway Traffic Safety Administration. Crowdsourcing Speed Limits and the Question of
7. National Household Travel Survey (2017). Number of bibliography/2188. Fatality Analysis and Reporting System. Retrieved Safety. Transportation Research Record. Retrieved
Person Trips by Mode. Retrieved from: https://nhts.
from: https://www.nhtsa.gov/es/research-data/ from: https://doi.org/10.1177/0361198120928995.
ornl.gov/ person-trips. 21. Tefft, B.C. (2011). Impact Speed and a Pedestrian’s
fatality-analysis-reporting-system-fars.
Risk of Severe Injury or Death. AAA Foundation 46. Federal Highway Administration (2012). Methods and
8. National Highway Traffic Safety Administration. for Traffic Safety. Retrieved from: https:// 34. National Highway Traffic Safety Administration Practices for Setting Speed Limits: an Informational
Fatality Analysis and Reporting System. Retrieved aaafoundation.org/impact-speed-pedestrians- (2018). Traffic Safety Facts: Pedestrians. Retrieved Report. Retrieved from: https://safety.fhwa.dot.gov/
from: https:// www.nhtsa.gov/es/research-data/ risk-severe-injury-death/. from: https://crashstats.nhtsa.dot.gov/Api/Public/ speedmgt/ref_mats/fhwasa12004.
fatalityanalysis-reporting-system-fars.
ViewPublication/812681.
22. Ibid. 47. California state law requires localities to evaluate
9. Stanford Open Policing Project. Retrieved from:
35. National Highway Traffic Safety Administration 85th percentile speeds on a given street every seven
https://openpolicing.stanford.edu/. 23. Transportation Research Board (2012). NCHRP
(2015). New Car Assessment Program years in order for the speed limit to be enforceable.
Report 600: Human Factors Guidelines for Road
10. National Traffic Safety Board (25 July, 2017). (Docket No. NHTSA–2015–0119). Retrieved According to the law, the city must identify the 85th
Systems. Retrieved from: http://onlinepubs.trb.
Reducing Speeding-Related Crashes Involving from: https://www.federalregister.gov/ percentile speed on the street and set speed limits to
org/onlinepubs/nchrp/nchrp_rpt_600second.pdf,
Passenger Vehicles. Retrieved from: https://www. documents/2015/12/16/2015-31323/new-car- the nearest multiple of five.
pp. 5-12.
ntsb.gov/safety/safety-studies/Documents/SS1701. assessment-program.
48. California Highway Patrol.Statewide Integrated
pdf. 24. American Association of State Highway and
36. Ulrich, Lawrence (12 September, 2019). S.U.V. vs. Traffic Records System. Retrieved from: http://
Transportation Officials (2001). A Policy on
11. Organisation for Economic Co-operation and Sedan, and Detroit vs. the World, in a Fight for iswitrs.chp.ca.gov/Reports/jsp/userLogin.jsp/.
Geometric Design of Highways and Streets.
Development. Road accidents. Retrieved from the Future. The New York Times. Retrieved from:
Retrieved from: https://www.bestmaterials.com/ 49. Hu, W. and J. Cicchino (2019). Lowering the speed
https://data.oecd.org/transport/road-accidents. https://www.nytimes.com/2019/09/12/business/
PDF_Files/geometric_design_highways_and_ limit from 30 to 25 mph in Boston: effects on vehicle
htm. suv-sedan-detroit-fight.html.
streets_aashto.pdf, pp. 56. speeds. Insurance Institute for Highway Safety.
12. Smart Growth America (2019). Dangerous by Design. 37. International Transport Forum (2019). Road Safety Retrieved from: https://www.iihs.org/topics/
25. National Highway Traffic Safety Administration
Retrieved from: https://smartgrowthamerica.org/ Annual Report 2019: Sweden. Retrieved from: bibliography/ref/2168.
(August 2015). Safety Facts. Retrieved from:
app/uploads/2019/01/Dangerous-by-Design-2019- https://www.itf-oecd.org/sites/default/files/
https://one.nhtsa.gov/nhtsa/Safety1nNum3ers/ 50. Fridman, L., Ling, R., Rothman, L. et al. (2020). Effect
FINAL.pdf. sweden-road-safety.pdf.
august2015/S1N_Aug15_Speeding_1.html. of reducing the posted speed limit to 30 km per hour
13. Cusick, Daniel (21 Jan, 2020). “Past Racist ‘Redlining’ 38. US Department of Transportation, Bureau of on pedestrian motor vehicle collisions in Toronto,
26. University of Pennsylvania School of Engineering
Practices Increased Climate Buden on Minority Transportation Statistics (2014). Table 2-9: U.S. Air Canada - a quasi experimental, pre-post study. BMC
(April 2015). Vehicle Stopping Distance and Time.
Neighborhoods”. E&E News. Retrieved from: https:// Carrier Safety Data [table]. Retrieved from: https:// Public Health 20, 56. Retrieved from: https://doi.
Retrieved from: https://nacto.org/wp-content/
www.scientificamerican.com/article/past-racist- www.bts.gov/archive/publications/national_ org/10.1186/s12889-019-8139-5.
uploads/2015/04/vehicle_stopping_distance_
redlining-practices-increased-climate-burden-on- transportation_statistics/table_02_09.
and_time_upenn.pdf. 51. Seattle DOT (July 2020). Speed Limit Case
minority-neighborhoods/.
39. National Civil Aviation Review Commission Archive Studies. Retrieved from: https://www.seattle.
27. Layton, Robert, and Karen Dixon (April 2012).
14. Goddard, Tara et al. (August 2015). Racial gov/Documents/Departments/SDOT/VisionZero/
Stopping sight distance. Retrieved from: https:// 40. Josephs, L (13 Feb, 2019). The Last Fatal US Airline
bias in driver yielding behavior at crosswalks. SpeedLimit_CaseStudies_Report.pdf.
cce.oregonstate.edu/sites/cce.oregonstate.edu/ Crash Was a Decade Ago. Here’s Why Our Skies are
Transportation Research Part F: Traffic Psychology files/12-2-stopping-sight-distance.pdf. Safer. CNBC. Retrieved from: https://www.cnbc. 52. Federal Highway Administration. Curb Radius
and Behaviour, 33, pp 1-6. Retrieved from: https://
com/2019/02/13/colgan-air-crash-10-years-ago- Reduction. Retrieved from: https://safety.fhwa.dot.
www.sciencedirect.com/science/article/abs/pii/ 28. National Association of City Transportation
reshaped-us-aviation-safety.html. gov/saferjourney1/library/countermeasures/09.htm.
S1369847815000923. Officials. (2013). Urban Street Design Guide. New
York, NY: Island Press.
24 25The Need NACTO City Limits
SAN FRANCISCO
Photo: SFMTA
2
The
Tools
26The Tools NACTO City Limits City Limits NACTO The Tools
Tools to Change Speed Limits Authority to Change Speed Limits
The tool or combination of tools a city uses or state legislation determines statewide
There are three primary tools for will depend on their authority to set speed speed limit setting requirements. In the
setting speed limits in urban areas. limits. In some cases, state law already absence of legislative or administrative
grants cities authority to set speed limits that requirements, city authority depends on
comply with the guidance in City Limits. In engineering practice or law at the city level.
others, state departments of transportation
Default Speed Limits* If the city has...
Set default speed limits
State-granted If possible, start by setting citywide default speed
on many streets at once.
authority to lower limits at 25 mph or below.
speed limits through
If desired or more politically feasible, set default speed
a locally-defined
limits by category of street (e.g., 25 mph on arterials, 20
process or across
mph on non-arterials).
many streets at once.
*Applicable on all streets—
major, minor, and shared Use a Safe Speed Study (see page 58) to lower speed
streets / alleys limits below the citywide or category default on high-
crash or otherwise high priority corridors. Consider using
a Safe Speed Study to evaluate a batch of similar streets
to lower speed limits on many streets of one type all at
once (e.g., local streets).
Slow Zones
Designate slow zones
in sensitive areas. Designate slow zones. Slow zones can be linear
(along a street) or cover all streets within a specific
neighborhood or business district.
If state or local legislation prevents any of the above,
but conducting Safe Speed Studies and lowering default
limits is desired, seek the authority to do so.
If the city has...
Corridor Speed Limits* Limited authority Seek a written change in practice (leveraging City
to lower speed limits Limits may help).
Set corridor speed limits on
using a locally-
high priority major streets
defined process or
using a Safe Speed Study
across many streets Request that some streets be exempt from the 85th
(see page 58).
at once. percentile requirement (e.g., streets near schools or other
sensitive areas like parks or neighborhood downtowns).
*Applicable on
major streets only
Once the authority is established, see actions above.
28 29The Tools NACTO City Limits City Limits NACTO The Tools
Combining Tools
Cities that have authority to set default speed to use a locally-defined process such as the
limits have a number of options to improve Safe Speed Study method outlined on page
safety on their streets. In some cities, setting 58, that is different from the 85th percentile
the default limit citywide is the most effective method. In some cases, cities have used this Cities can combine these proactive speed management
approach. Citywide defaults provide a uniform, same tactic to set default citywide or category- strategies to create safe conditions for their city.
predictable limit that applies everywhere. based speed limits by conducting “bulk studies”
They are relatively easy to implement and on a representative sample of similar streets in
easy to explain to the public. Citywide limits order to assess the appropriate speed for that Default
Slow Zones Limit
can be combined with slow zones and with category of street.
EXAMPLE COMBINATION: CITY A (e.g., schools, Priority
corridor limits on specific corridors to address
conditions where a speed lower than the
In the states where jurisdictions must set speed
limits on most streets based on 85th percentile City A has explicit authority to set default
parks)
25 Corridors
citywide default is necessary. MPH
In cities where there is clear differentiation
speeds, some cities have requested exemption
from using the 85th percentile for specific streets
speeds and has chosen to set a citywide
default limit of 25 mph on all streets. In
20 20
MPH MPH
between major arterial streets and local or (for example, streets identified in a high-injury addition, they have identified a few high-
minor streets, cities may choose to set speeds network analysis). In these places, robust crash, crash corridors and have set 20 mph corridor
by street type or category. Category-based fatality, and injury data collection is particularly limits on those streets to reduce fatalities
limits allow cities to address significantly important to make the case for exemptions. and injuries. They also have established 20
different street contexts but still create mph slow zones in key areas around schools
In almost all states, cities have authority to or parks to provide additional protection for
a predictable regulatory environment for
create school slow zones. For example, in children.
drivers. Like citywide defaults, category-based
California, which codifies the use of the 85th
defaults can be combined with slow zones and
percentile method to determine and enforce
with corridor limits on specific streets.
speed limits on streets across the state, the
Category 1: Category 2:
In some states, cities do not have explicit Vehicle Code allows all local jurisdictions to EXAMPLE COMBINATION: CITY B Arterial Non-Arterial
authority to set their own default speed limits. lower speeds in school zones that meet specific
These cities have different playbooks for criteria. In 2019, Sacramento used this authority City B has explicit authority to set default
aligning speed limits with their safety goals. to reduce speed limits from 25 to 15 mph on 225 speed limits and has clear differentiation 25 20
street segments across the city, even without between major or arterial streets and minor MPH MPH
In states where the process for engineering
the explicit authority to reduce default speeds or local streets. They have chosen to set
studies is not codified in state law or practice,
citywide. category speed limits at 25 mph for arterials
cities have asked for (or assumed) permission
and 20 mph for non-arterials. Like City A,
they may choose to also establish slow zones
in key areas.
SACRAMENTO
EXAMPLE COMBINATION: CITY C Category 1: Category 2: Priority
Residential Arterial Streets
City C does not have explicit authority to
set default speeds. The state requires a
speed study but does not lay out an explicit
20 25 20
MPH MPH MPH
process. They have chosen to conduct a
bulk engineering study and to use a locally-
defined process for setting speeds by street
category. At the same time, using authority
to set speed limits on a case-by-case basis,
Photo: City of Sacramento
they have conducted a Safe Speed Study to
determine appropriate speed limits for a few
priority corridors.
30 31The Tools NACTO City Limits City Limits NACTO The Tools
RECENT NOTABLE
LEGISLATIVE CHANGES OREGON MINNESOTA
Implementing the speed limit tools Oregon (Senate Bill 558) allows all cities in Minnesota Statute (Section 169.14, Subd. 5h - Speed
recommended in this guidance may require the state to establish a 20 mph speed limit limits on city streets) allows cities to establish
state-level legislative permission. A growing on all non-arterial streets in residence speed limits on city streets based on the city’s safety,
group of US states have passed legislation districts under city jurisdiction. Rule 734- engineering, and traffic analysis. Speed limits must be set
granting cities the flexibility to set safer 020-0015 allows the use of 50th percentile in a consistent and understandable manner.
speed limits. These supportive policies studies instead of 85th percentile studies
generally take one of two forms: on non-residential streeets.
Authority to set context-
sensitive speed limits using
a locally-defined process.
Several states have passed laws that
enable cities to create, adopt, and utilize
an approach for setting urban speed limits
that places safety as the top priority. Cities
that leverage this authority do so in different
ways, often by lowering default limits on MASSACHUSETTS
some or all streets and also by updating
local engineering guidance to redefine Massachusetts (MGL c. 90 § 17C) allows
speed study procedures. “thickly settled” cities and towns to adopt a
WASHINGTON STATE 25 mph default speed limit by ordinance for
all streets unless otherwise posted. Cities and
Washington State has two pieces of towns can also set 20 mph safety zones, which
enabling legislation that, together, allow they can use their own criteria to create.
cities to set safe speed limits:
RCW 46.61.415 allows local agencies to
establish/alter maximum limits on local
streets. NEW YORK STATE
Authority to reduce default
New York State Assembly Bill 10144/Senate
speed limits. WAC 468-95-045 is a modification to
Bill 7892 amended section 1642 of the Vehicle
the State MUTCD that provides local
Some states have passed laws that explicitly and Traffic Law to allow New York City to set a
jurisdictions with considerations about
allow cities to lower their default citywide speed limit of 25 miles per hour, down from 30
what requirements they need to meet to
speed limits (e.g., from 30 mph to 25 mph) or mph, on streets that are not part of the State
revise the posted speed limit.
speed limits on a specific category of streets highway system. This was followed by NYC
(e.g., “residential streets” at 20 mph). Local Law 54 of 2014, which enacted a citywide
speed limit of 25 mph unless otherwise posted.
32 33The Tools NACTO City Limits City Limits NACTO The Tools
Case Studies
POLICY HURDLES
A city’s ability to change speed limits is impacted by rules and practices around
enforcement, signage, and design requirements.
in Lowering Speed Limits
NEW YORK
Enforcement
A city’s ability to enforce the posted speed limit depends on whether
speed limits in the state are Absolute, Prima Facie, Basic Speed Law,
or a combination of the three. When drivers are ticketed in a state
with absolute speed limits, the ticket will typically stand on face
value. In states with prima facie, or presumed, speed limits, drivers
Photo: Logan Hicks
can contest tickets in court on the basis that their speed was safe for
the conditions. In basic speed law states, drivers are required only to
travel at a safe speed, regardless of the posted speed limit. A growing Recognizing the importance of lowering speed limits to improve safety, a number of cities
body of evidence shows that drivers respond to posted speed limits have successfully amended their speed limits in recent years. The four cities highlighted
even without changes to enforcement; cities may want to make speed below present interesting lessons learned for other municipalities looking to lower speed
limit changes even when enforcement is difficult. limits on their streets.
Signage SEATTLE
In some states, a city must install a sign on every block if the posted
In 2016, Seattle lowered its default speed limit from 25 to 20 mph on neighborhood streets
speed limit is anything other than the citywide default. This is feasible
and from 30 to 25 mph on arterials. The City has also begun to reduce speed limits within
when the city lowers the limit on a small number of segments, but
urban villages, where lots of people walk, bike, drive and use transit.
becomes prohibitively expensive at a large scale (e.g., across all
residential streets). Resources: Seattle DOT Speed Limits Website, Seattle DOT Blog
NEW YORK CITY
Design
In some states, cities must implement physical design changes to In 2014, New York City lowered its default citywide speed limit from 30 to 25 mph, which
streets in order to justify lower speed limits. Requiring engineering complemented a Neighborhood Slow Zone program implemented in 2011.
changes before cities can change the posted limit can make it difficult
Resources: 2014 NYC Vision Zero Action Plan, Borough Pedestrian Safety Action Plans,
for cities to change speed limits on a large number of streets because
Families for Safe Streets
of the cost. Other cities must reduce speed limits before they can
make design changes, since the design speed is set in relation to the
posted speed on a given street. CAMBRIDGE
In 2016, the City of Cambridge lowered its default citywide speed limit from 30 to 25 mph. In
the years since, Cambridge has leveraged authority to further reduce speed limits to 20 mph
in Safety Zones to reduce speed limits to 20 mph on nearly every street in the city.
Resources: City of Cambridge Speed Limits Website
PORTLAND
In 2018, Portland lowered the default speed limit on residential streets from 25 mph to 20
mph. This change complements 20 mph speed limits in business districts.
Resources: Portland Bureau of Transportation Speed Limits Website, 50th Percentile
Allowance on Non-Residential Roads
34 35You can also read
