Guidelines for the Design and Application ofSpeed Humps

ISummary of a Proposed Recommended Practjce
Guidelines for the Design and
Application of Speed Humps
BY ITE TECHNICAL COUNCIL TASK FORCE ON SPEED HUMPS
This is a summary of a report that
being proposed as a recommended
is
practice of the Institute of
Transportation Engineers. Copies of
the complete proposed recommended
practice are available from the ITE
Bookstore (Publ. No. RP-023).
Comments are being sought on
this proposed recommended practice
to assist in its consideration for adoption
as a recommended practice of
the Institute of Transportation
Engineers. Comments or questions
and any requests for public hearing
should be submitted by August 1,
1993, to the director of Technical
Programs, Institute of Transportation
Engineers, 525 School St., S.W., Suite
410, Washington, DC 20024-2729
USA, telephone 202/554-8050; fax
202/863-5486.
Comments and suggested revisions
will be considered and addressed by
the task force before the submittal of
the proposed recommended practice
to the Institute’s Standards Approval
Board for final decision on adoption
as a recommended
Institute.
practice of the
This report was prepared by a special
task force appointed by the
Institute of Transportation Engineers
Technical Council in 1988. Members
of this task force were R. Marshall
Elizer Jr. (F) (chairperson); David E.
Barnhart, P.E. (M); Richard F.
Beaubien, P.E. (F); Bert Beukers,
P.E. (F); Ian C. Boyd, P.E. (F); John
P. Clement, P.E. (F); Charles E.
DeLeuw Jr. (M); William E. Hare,
P.E. (M); Jim Jarvis; William R.
McGrath, P.E. (H); Kenneth Melston,
P.E. (F); Jere E. Meridith, P.E. (F);
Andrew P. O’Brien (M); Sheldon I.
Pivnik (F); Thomas A. Sohrweide,
P.E. (A); Burton W. Stephens; Roy L.
Sumner (M); Douglas W. Wiersig
(M).
Certain individual volunteer members
of the Institute’s recommended
practice developing bodies are
employed by federal agencies, other
governmental offices, private enterprise
or other organizations. Direct
participation in these activities does
not constitute endorsement by these
government agencies or other organizations
or any of the Institute’s recommended
practice developing bodies
or any Institute recommended
practices that are developed by such
bodies.
This proposed recommended practice
has been developed in accordance
with formally adopted Institute
procedures designed to ensure that a
representative cross section of parties
Conversion Factors
To convert from IQ multiply by
ft m 0.3048
mph kmlh 1.609
jn. cm 2.54
is given an opportunity to provide
input. It should be noted that the proposed
recommendations are guidelines
and do not constitute an exclusive
set of acceptable procedures.
They are not necessarily intended to
supersede specific local, regional or
state requirements, although those
agencies might wish to modify their
requirements as a result of reviewing
these recommendations. They will,
however, assist public agencies, as
well as private property owners, in
understanding the design and application
issues associated with the possible
use of speed humps, a roadway
geometric design feature intended to
physically reduce vehicle operating
speeds.
Speed humps are in widespread
use throughout the United States,
Europe, Australia and other countries.
The lack of uniform guidance,
comprehensive research and heavy
reliance on individual judgment has
led to hump-type installations that
incorporated poor designs, improper
roadway geometric coordination,
poor choice of construction materials
or methods and absence of needed
signs and markings. The safety of
speed humps and their ability to perform
their intended use is directly
contingent upon their proper design
and application. When it is determined
that a residential traffic management
problem exists, and that
speed humps are an appropriate tech-
MAY 1993 ● ITE JOURNAL ● 11

nique to reduce or eliminate the
problem, this ITE proposed recommended
practice will assist in establishing
locally adopted guidelines for
the design and application of those
geometric design features.
Until the 1970s, the effects of
motor vehicle traffic on the quality of
urban residential environments were
largely neglected as a serious transportation
problem. In the past
decade, however, a number of converging
forces have increasingly
brought these effects to the attention
of both citizens and local transportation
officials. Many local governments
are finding themselves under
intense pressure to reduce the speed
and volume of traffic on neighborhood
streets to address both real and
perceived safety and quality of life
issues.
While proper transportation planning,
subdivision layout and residential
street design are the most effective
methods of avoiding residential
traffic problems, these goals are not
always achievable. Where problems
exist, traffic management programs
have been demonstrated successfully
as effective strategies for addressing
residential safety and quality of life
issues. They remain, however, a challenging
task from the engineering,
political and institutional standpoints.
Traffic management strategies
employed to address residential traffic
concerns generally can be assigned
to four basic categories:
● Establishing and enforcing general
laws and ordinances.
● Educating residents and motorists.
● Installing traffic control devices.
● Installing roadway geometric design
features.
Solving residential traffic problems
often involves an approach that
employs all of these strategies. The
final traffic management program for
any area must be developed on a
case-by-case basis using local engineering
judgment in conformance
with local regulations and ordinances.
This article summarizes “Guidelines
for the Design and Application of
Speed Humps,” a proposed recommended
practice of the Institute of
Transportation Engineers. The proposed
recommended practice considers
speed humps as a roadway geometric
12 ● ITE JOURNAL ● MAY 1993
Figure 1. The difference between a speed bump and a speed hump.
design feature intended to physically
reduce vehicle speeds. Other types of
geometric design features that are not
addressed in this document, but that
could be considered in a residential
traffic management program, are raised
intersections, rumble strips, pavement
width reductions, traffic circles, median
barriers, diverters, left-turn channelization
and street closures. Geometric
design features should only be installed
after less restrictive strategies have
been considered, and in no event
should their use be intended to allow or
encourage the use of public streets as
playgrounds.
ITE has recognized the need for
providing transportation professionals
and community leaders with strategies
and techniques for creating compatible
relationships between residential
neighborhoods and streets. In an
attempt to address that need, the
Institute has developed Residential
Street Design and Traffic Control, a
book that fully discusses the history
and causes of residential traffic problems.
It provides information to assist
transportation professionals in understanding
and finding solutions to these
issues.
The proposed recommended practice
is presented in six chapters. The
following information briefly summarizes
the key recommendations within
each of these chapters.
Chapter 1: Introduction
Included in this chapter is a statement
defining the purpose of the proposed
recommended practice, which
is to provide guidelines for the design
and application of speed humps,
which are intended to control vehicular
traffic speeds along a roadway.
They consist of raised pavement con-
structed or placed in, on and across or
partly acro& a roadway to reduce the
speed of vehicles traveling along that
roadway. While there might be certain
side effects to speed hump installations,
such as traffic diversion to
other streets, that is not their primary
intended purpose.
Speed Humps vs. Speed Bumps
A speed hump is differentiated
from a speed bump as shown in
Figure 1. Speed humps normally have
a maximum height of 3 inches to 4 in.
with a travel length of about 12 feet.
Speed bumps, commonly used in
parking lots and on some private
roadways, are generally from 3 in, to
6 in, in height with a length of 1 ft to 3
ft.
From an operational standpoint,
humps and bumps have critically different
impacts on vehicles. Within
typical residential speed ranges,
humps create a gentle vehicle rocking
motion that causes some driver discomfort
and results in most vehicles
slowing to near 15 miles per hour at
the hump and 20 mph to 25 mph
between properly spaced humps in a
system. At high speeds, a hump acts
as a bump and jolts the vehicle suspension
and its occupants or cargo.
A bump, on the other hand, causes
significant driver discomfort at typical
residential speeds, and generally
results in vehicles slowing to 5 mph or
less at the bump. At high speeds,
bumps tend to have less overall vehicle
impact because nonrigid suspensions
quickly absorb the impact
before the vehicle body can react. In
general, bicycles, motorcycles and
other vehicles with rigid or near-rigid
suspensions are more susceptible to
damage and loss of control from
humps and bumps than vehicles with

0 0,64 1.22 1.75 2.22 2,64 3.00 3.31 3,56 3,753.89 3.97 4.00”~ 4“ Speed Hump
0 0.56 1.07 1,53 1.94 2.31 2.63 2.89 3.11 3.283,40 3.46 3.50”~ 3.5” Speed Hump
O 0.48 0.92 1.31 1.67 1.86 2,25 2.46 2.67 2.81 2,92 2.98 3.00”~ 3“ SDeed HumD
Figure 2. Typical speed hump dimensions (parabolic 4-in., 3.5-in. and 3-in.).
flexible suspensions. However, speed
humps generally present less of a risk
to those vehicles than speed bumps.
Where designed and installed with
proper planning and engineering
review, speed humps have been found
to be effective at reducing vehicle
speeds without creating accidents or
increasing accident rates, In fact,
some studies have concluded that
speed hump installations have actually
reduced accident rates on residential
streets. Also, the ITE Task Force
found no evidence in the material
reviewed for this report indicating
that properly designed and installed
speed humps have caused or contributed
to accidents or increased
accident rates.
Within the United States, speed
bumps of varying design routinely
have been installed on private roadways
and parking lots without the
benefit of proper engineering studies
regarding their design, placement and
impact. Speed humps, on the other
hand, have evolved from extensive
research and testing and have been
designed to achieve a specific result
on vehicle operations without imposing
an unreasonable or unacceptable
safety risk. The guidelines for speed
humps presented in this proposed
recommended practice are primarily
based on those experiences.
Speed Hump Development and
Experience
Speed humps originally were
developed in the early 1970s by the
Transport and Road Research
Laboratory (TRRL) in Great Britain.
TRRL first tested various hump sizes
and shapes and several vehicle types
operating over a range of speeds.
From this work, the TRRL parabolic
profile hump was developed (see
Figure 2). Since then, speed humps
have been tested extensively in
Europe as well as Australia, New
Zealand, the United States and other
countries. The U.S. Federal Highway
Administration also performed offroad
testing of speed humps in St.
Louis in 1979. Based upon their findings,
they recommended proceeding
with public street tests. An emerging
number of cities in the United States
and Canada have begun to use speed
humps based on this research and
experience. For example, in
November 1983, a subcommittee of
the California Traffic Control
Devices Committee issued a report
endorsing the prudent use of speed
humps on public streets.
The results of speed hump
research and testing can generally be
summarized as follows:
●
●
●
●
Traffic speeds are decreased at the
humps and at locations between
properly spaced successive humps.
Speeds of the fastest drivers are
affected as well as those of average
drivers. The speed distribution
generally narrows with the greatest
effect on higher vehicle speeds.
A single hump will only act as a
point speed control. To reduce
speeds along an extended section
of street, a series of humps usually
is needed.
Speed humps often divert traffic to
other streets, especially in those
situations where a significant
amount of traffic is using the street
as a shortcut, detour or overflows
from a congested collector or arterial
roadway. Volume reductions
also are affected by the number
and spacing of humps and the
availability of alternative routes.
Speed and volume modifications
caused by humps tend to remain
constant over time.
●
●
●
●
●
●
Speed humps have not been found
to pose a traffic safety hazard
when properly designed and
installed at appropriate locations.
In fact, accident experience generally
remains stable or decreases
because of reduced speeds and volume,
thereby improving the inherent
safety of the particular street
or residential area.
If the humps are successful at
reducing speeds, there is probably
little net change in road noise or
possibly even a reduction in noise
levels. Traffic noise generally
decreases with fewer vehicles and
lower speeds, but noise can
increase at the hump, particularly
if a significant number of trucks
use the street.
Adequate signing and marking of
each speed hump is essential to
warn drivers of speed hump presence
and guide their subsequent
action.
A need to slow for speed humps
tends to have a negative impact on
air quality and energy consumption
assuming traffic volumes
remain constant. For comparison
purposes, this impact is typically
less than the effects of a stop sign
installation.
Large trucks, buses and emergency
vehicles must pass over humps at
relatively low speeds or significant
jolts to the vehicle, discomfort or
injury to occupants, and jostling of
cargo might be experienced. Speed
humps have been used to deter
trucks and larger vehicles from
using particular streets.
The majority of local street residents
normally support speed
hump installations and endorse
their continued use.
It also should be noted that some
MAY 1993 ● ITE JOURNAL “ 13

speed hump installations in the
United States and other countries
have been unsuccessful and ultimately
modified or removed. Factors
resulting in their removal have
included the following:
●
●
●
●
●
●
●
●
●
Residents’ dissatisfaction with the
TRRL hump design and its perceived
inability to dramatically
slow vehicles or reduce traffic volume
to a desired level.
Local policy decision to favor traffic
circulation needs over residents’
quality of life concerns.
Undesired traffic diversion to other
residential streets.
Aesthetics of the humps and associated
signs and markings.
Increased noise level at the home
caused by vehicle rocking and
acceleration/deceleration.
Impacts on street maintenance
functions such as sweeping and
snow- plowing.
Concerns with impacts to emergency
vehicle response.
Concerns of increased exposure to
damage claims and lawsuits.
Limited funding for the initial
installation or continued maintenance
cost of the hump and its
traffic control devices.
Chapter 2: Guidelines
for Speed Hump Use
This chapter outlines the primary
considerations and criteria for the use
or nonuse of speed humps. The following
summarizes the key recommendations
of the chapter.
●
●
●
●
●
A traffic engineering study, including
consideration of alternative
traffic control measures, should
precede any installation.
Speed humps should only be
installed on local two-lane residential
streets with less than 3,000
vehicles per day, with a posted or
prima facie speed of 30 mph or
less.
Hump locations should be closely
coordinated with street geometry
and grades.
Speed humps should not be
installed on streets with significant
amounts of emergency vehicles,
transit or long wheelbase vehicles.
Support from a documented major-
14 ● ITE JOURNAL ● MAY 1993
ity of affected residents should be
obtained before any installation.
Chapter 3: Community
Relations and
Administrative Procedures
This chapter addresses a number
of items relating to establishing local
procedures, policies and regulations
regarding speed humps. The specific
sections address the following:
The need to adopt supporting ordinances
or regulations.
Establishment of speed hump
request and evaluation procedures.
Coordination with emergency service
priorities, utilities and other
key agencies.
The need to adopt procedures for
follow-up evaluations and
removal, if necessary.
Funding responsibilities for installation,
maintenance and removal,
if necessary.
Chapter 4 Design and
Construction
Considerations
Once the decision has been made
to employ speed humps in a residential
traffic management program, this
chapter assists-in identi~ying the
essential design and construction considerations.
Items discussed are:
●
●
●
●
●
●
Dimensions and cross sections for
the recommended parabolic profile
hump (12 ft length, with a center
of 3 in. to 4 in.).
Relationship between hump spacing
and impacts on vehicle speeds.
Coordination with traffic control
devices, street lighting, drainage,
utilities and on-street parking.
Treatment of humps ends for
curbed and noncurbed streets.
Supporting signs and markings.
Construction materials and procedures.
Chapter 5: Monitoring
and Evaluation
This chapter identifies and discusses
monitoring activities and evaluation
processes necessary to fully
understand the impact and effective-
ness of speed hump use. The chapter
addresses:
●
●
●
●
●
The need for on-site observations
after installation.
Follow-up studies to evaluate
speeds, stop sign obedience, travel
time inputs, accident potential and
residentldriver opinions.
The potential need for noise, vibration
and air quality analysis in
environmentally sensitive areas.
The positive or negative impacts on
pedestrian, bicycle and social activity.
The possibility of a user cost analysis
to determine the economic
inputs on traffic.
Chapter 6: Other
Considerations
Addressed in this chapter are a
series of issues related to speed hump
use that also should be considered in
establishing a speed hump program.
They are:
● Liability for tort and vehicle damage
claims.
● Coordinating humps with pedestrian
crossing coordination.
● Incorporating humps in new street
design.
● Ability to meet enforcement and
maintenance needs.
Chapter 7: Source
Materials
This chapter lists, in reverse
chronological order, about 150 documents
related to speed humps, bumps
and other residential traffic management
features. Many of these documents
have been used as references
by the ITE Task Force in the preparation
of this proposed recommended
practice, while others have been
included as potential references for
anyone interested in further research
of speed humps or related features.
Conclusions
Extensive research and use
throughout Great Britain, Australia,
the United States, Canada and other
countries indicates that the use of a
properly designed speed hump or
speed hump system, installed using

the proper engineering analysis and
judgment, can be a useful geometric
design feature to manage traffic
speeds on local residential streets.
Speed humps have been found, in
general, to reduce traffic speed, volumes
and accidents depending upon
the site-specific circumstances of the
installation. In addition, they discourage
through traffic from using a local
street as an alternative route to inconvenient
or congested arterial and collector
systems. Despite concerns of
liability, vehicle damage and emergency
vehicle impacts, these problems
either have not occurred or have been
found to be minor considering the
positive aspects of humps.
However, speed humps are not a
cure-all for residential street traffic
problems and should be applied only
where sound engineering judgment
justifies their use. Other passive and
active devices and techniques should
be considered and possibly tested to
determine if less restrictive forms of
traffic management will address these
concerns. Speed humps should not be
considered an option to good residential
planning and subdivision street
design, nor should they be used to
convert streets to playgrounds or otherwise
encourage pedestrian activity
in public streets.
The lack of uniform guidance and
heavy reliance on individual judgment
has led to hump-type installations
that incorporated poor design,
improper roadway geometric coordination,
poor choice of construction
materials and methods, and absence
of needed signs and markings. The
safety of speed humps and their ability
to perform their intended use is
directly contingent upon their proper
design and application. When it is
determined that speed humps are an
appropriate traffic management technique,
this ITE proposed recommended
practice will assist in the
design, application and evaluation of
those geometric design features. 1
R. Marshall EIizer
Jr., P. E., is the
director for the City
of Modesto Public
Works and TransportationDepartment
in Modesto,
California. He was the chairperson of
ITE Technical Council Task Force on
Speed Humps, and he is a Fellow of
the Institute.