Document 157453

I
Summary of a Proposed Recommended
Practjce
Guidelines for the Design and
Application of Speed Humps
BY ITE TECHNICAL COUNCIL TASK FORCE ON SPEED HUMPS
his is a summary of a report that is
proposed as a recommended
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
practice
of the
Institute.
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
T being
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
To convert from
ft
mph
jn.
Factors
IQ multiply by
0.3048
m
1.609
kmlh
2.54
cm
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 techMAY 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
recomSpeed Humps,” a proposed
mended practice of the Institute
of
Transportation
Engineers.
The proposed recommended practice considers
speed humps as a roadway geometric
12
●
ITE JOURNAL
●
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.
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
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-
MAY 1993
*.
0
0,64
0
O
0.56 1.07 1,53 1.94 2.31 2.63 2.89 3.11 3.283,40
0.48 0.92 1.31 1.67 1.86 2,25 2.46 2.67 2.81 2,92
1.22
1.75
2.22
2,64
3.00
3.31
3,56
3,753.89
3.97
4.00”~
3.46 3.50”~
2.98
3.00”~
4“ Speed Hump
3.5” Speed Hump
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.
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:
●
●
●
Speed Hump
Experience
Development
and
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
●
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
●
ity of affected residents should be
obtained before any installation.
ness of speed hump use. The chapter
addresses:
●
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-
●
●
●
●
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 activit y.
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
MAY 1993
—
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 Transportation
Department in Modesto,
California. He was the chairperson of
ITE Technical Council Task Force on
Speed Humps, and he is a Fellow of
the Institute.
Tips from Budget Heros
WhoBob Tingerthd, Traffic Op., [email protected] of St. Paul, MN
St. Paul end OMJC go beokto 1988- OMJO’efirst full year in business.
We buy from end sell to S. Paul on a regular basis and save the city
thouaande of dollars. Items which the city haa ordered induda type 170
controllers(saving $400 per unit compared to new), eignal brackets and
herdwere, and OMJC’S exclusive signal haad cover.
St. Peul has boughtover 100 signal covers in the peat ebryeara. All
have seen repeated uee, WW the originalcovers purchased in 1988 still
on the street. Bob suggeststheir use on any projectin the city where a
signal is installed, but not in service. This is to comptywith section
4519 of the MUTCD. Consideringthat the dd ‘standard’ of signal
covers wee a plastic garbege bag stuck on with duct tape, Bob feels
that the reduced maintenance coats (garbage begs had to be replaced
frequently) and reduced riskto the city have more then justifiedthe
expense of the covers. Added to that, the covers Iodr a lot more
professionalthan garbage bags, which helps enhance the image of his
*.
An addad bonus for St. Paul is that when they buy raoondiionad
DrOdUCtS from OMJC. thev are as kind to the environmentas to their
budget. Baving money end
radudng waste at the same time
makes Bob and St. Paul smile.
w
*
Pam-.
n
Phale 1-aoG7rEeass
FAX 31923R1S54
MAY 1993
●
ITE JOURNAL
“ 17