NMA Traffic Calming Fact Sheet ( PDF )
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By Kathleen Calongne

Traffic calming devices, such as speed humps and traffic circles are spreading to communities across the United States, without regard to their risks. The U.S. Department of Transportation (USDOT) has avoided the examination of the problems associated with intentionally imposing vertical and horizontal deflection on vehicles and vehicle passengers, in order to encourage the proliferation of devices on city streets.

Deflection devices built to slow passenger vehicles, create even greater delays to emergency response vehicles. The longer wheel-base, stiff suspension, high vehicle weight, as well as the sensitive equipment and injured victims transported by these vehicles, requires drivers to slow almost to a stop to negotiate the devices safely.

An unethical attempt has been made to silence the objections of rescue personnel to delays to emergency response by deflection devices. Fire chiefs, as city appointees, fear professional retribution and often will not voice concern until the level of risk becomes intolerable. Emergency calls are not the rare events some members of transportation and city staff would like to believe. The City of Houston, Texas for example, responds to an average of 150,000 emergency medical calls and 100,000 fire calls per year. There is an average of 250,000 deaths from sudden cardiac arrest (SCA) alone each year in the United States. American Heart Association (AHA) statistics indicate that 90% of these incidents occur outside of the hospital environment. By comparison, there are approximately 5,000 pedestrian deaths per year in the United States. Few of these occur on local neighborhood streets. A ten-year study of pedestrian deaths by the U.S. Department of Health and Human Services, 1982 – 1992 found 35% of pedestrian victims were intoxicated. National Highway Traffic Safety Administration (NHTSA) statistics, Safety Facts 2000, found similar results with intoxication on the part of 31% of pedestrian victims. AHA statistics for SCA, show survivability is directly related to the response times of cities. For example, an AHA study in 1996 showed that Seattle with a response time of less than 7 minutes saved 30% of its SCA victims. New York, with an average response time of 12 minutes saved only 2%.

While delay from individual devices is sometimes measured, the cumulative effect of series of devices is often ignored. Series of devices turn seconds of delay into minutes, as vehicles fail to regain cruising speed between the devices. Calming devices impose permanent, 24-hour delays to emergency response, unlike traffic congestion which occurs periodically. A study conducted by the fire department of Austin, Texas, 1997, showed an increase in the travel time of ambulances of up to 100% transporting victims.

Members of city councils and transportation divisions often portray delay to emergency response by calming devices as simply a tradeoff for increased safety from speeding cars. They avoid making the analysis which shows which risk is greater. Ronald Bowman, a scientist in Boulder, Colorado developed an analysis to compare these risks. The results show that even minor delay to emergency response by calming devices imposes far greater risk on the community than vehicles, speeding or not. The result of Bowman’s analysis, showed a risk factor of 85 – 1 from an additional one minute of delay (predicted to result from the installation of all the devices proposed for the City of Boulder at the time) before one life might be saved by the devices — if it can be shown that the devices do save lives. Bowman’s analysis, based on the curve of survivability for victims of cardiac arrest and severe trauma (AHA) has been verified by a professional mathematician.

The Bowman analysis was applied to the City of Austin, Texas by Assistant Fire Chief, Les Bunte, with similar results.

The results of these analyses show that deflection devices are a tradeoff of the perception of increased safety from speeding vehicles for the real risk to citizen survivability from delay to emergency response. While the Institute of Transportation Engineers’ (ITE) Guidelines for the Design and Application of Speed Humps, 1997, states humps should never be placed on emergency response routes, humps and physical devices of all kinds have been installed on critical emergency response routes in cities where these projects exist. The proliferation of devices has resulted in temporary or permanent moratoriums on devices in cities such as Berkeley California, Boulder Colorado, Portland Maine and Portland Oregon.

People with disabilities complain of lasting pain and injury caused by traveling over deflection devices in vehicles. Significant testimony about the physical and psychological barrier deflection devices make to access to public rights-of-way has been given to the U.S. Access Board in Washington D.C.

Calming devices have been installed on streets to divide communities along racial and socioeconomic lines. The U.S. Department of Housing and Development (HUD) identified gates installed as part of a traffic calming project in Houston, Texas as discriminatory, ordering them removed. Gates were replaced with speed humps to create a similar, though less obvious, barrier between neighborhoods.

While calming devices are built on the premise they will reduce accidents, a comprehensive study commissioned by the ITE and the Federal Highway Administration (FHWA) on traffic calming projects in the United States concludes:

“Traffic calming in the U.S. is largely restricted to low volume residential streets. Collisions occur infrequently on such streets to begin with, and any systematic change in collision rates tends to get lost in the random variation from year to year. This limits our confidence in drawing inferences about safety impacts of traffic calming.”

(Traffic Calming: State of the Practice, Reid Ewing, 1999, P. 123)

The USDOT defines traffic calming devices as geometric design features of the roadway, rather than traffic control devices. The USDOT recommends standards for the design and warrants for the use of devices that are approved traffic control devices in the Manual on Uniform Traffic Control Devices (MUTCD). The definition of traffic calming devices as geometric design features of the road has allowed devices to proliferate on city streets as a decision of local governments.

An increase in accidents has occurred after some installations. Experimental speed humps placed on a street at a school in Portland, Maine registered an increase in accidents of 35%. Accidents increased 100% after the installation of an experimental traffic circle in Boulder, Colorado. However, the circle in Boulder and the humps in Portland remain on the street today.

People across the United States are opposing the installation of deflection devices on city streets that damage vehicles, injure vehicle passengers, increase pollution and gas consumption and delay emergency response. I have researched traffic calming projects since 1996, and have compiled my research into a 400-page report on the “Problems Associated with Traffic Calming Devices.”


These were the resources used for this article:


Reuben Castenada and Steven Gray, “Maryland Boy, 13, Dies in Fire at Friend’s Sleepover,” THE WASHINGTON POST, June 15, 1998 (Firefighter Stottlemeyer descends into basement to rescue child as flashover occurs forcing his exit from the home.)

Jen Chaney, “Fatal fire renews speed hump debate,” GAITHERSBERG GAZETTE, July 8, 1998 (Impact of delay caused by humps on street on rescue of child.)

Dwight Daniels, “Encinitas protesters’ parked vehicles hinder laying of speed bumps,” THE SAN DIEGO UNION TRIBUNE, Aug. 13, 1998

Editorial, “Meeting air standards Maine’s obligation too,” PORTLAND PRESS HERALD, October 17, 1997 (Ruling of EPA)

Editorial, “Street Fights,” THE HOUSTON CHRONICLE, July 12, 1994 (Closures foster exclusivity rather than community.)

Dan Feldstein, “Brown has 911 gate removed,” THE HOUSTON CHRONICLE, August 18, 1998 (“Closure denies emergency access.”)

Dan Feldstein, “Subdivision struggles with great barrier rift,” THE HOUSTON CHRONICLE, February 22, 1999

Kristen Green,”It’s neighbor vs. neighbor over Santee speed bumps,” THE SAN DIEGO UNION TRIBUNE, March 7, 2000

Kristen Green, “Disabled woman wins fight to remove speed bumps on her street,” THE SAN DIEGO UNION TRIBUNE, May 12, 2000

Jean-Martin Kuntscher, “Speed bumps cause ten times more air pollution,” ALLIANCE INTERNATIONALE DE TOURISME, FEDERATION INTERNATIONALE DE L’AUTOMOBILE, September 6, 1994

Lisa Marshall, “Circles called hazards,” THE DAILY CAMERA, December 12, 1996

Paul Marston, “Humps increase exhaust fumes,” UK NEWS, ELECTRONIC TELEGRAPH, January 14, 1998

Bruce Nichols, “Houston hits the brakes on speed-humps,” THE HOUSTON CHRONICLE, (“Deterrent for drivers raises worries about police, fire response.”) August 1, 1999

Amy Reinholds, “Whittier attempts mediation… Neighbors square off on traffic issue” THE DAILY CAMERA, January 21, 1997

Amy Reinholds, “Slip-sliding away at Pine St. traffic circle”, THE COLORADO DAILY, November 20, 1996

Judith Scherr, “Berkeley’s bumpy battle,” BERKELEY DAILY PLANET, March 27, 2000 (Berkeley Commission on Disability takes stand against humps.)

Mark Shanahan, “Federal government pulls funds from traffic-slowing experiment,” PORTLAND PRESS HERALD, August 18, 1998

Matt Schwartz, “HUD labels Dian Street gate discriminatory, asks removal,” THE HOUSTON CHRONICLE, October 15, 1998

Joanne B. Walker, “Speed bumps, tables meet legal obstacle,” ST. PETERSBURG TIMES, August 1998 (Judge Bennett rules in favor of 2 citizens who have filed suit against city for placing devices on streets used for traffic control which are not approved traffic control devices in the Manual on Uniform Traffic Control Devices.)

John Williams, “Street Warfare” (Intersection sealing brings racism calls.) THE HOUSTON CHRONICLE, July 10, 1994

John Williams, “Probe of bias and street closings looks at use of federal money,” THE HOUSTON CHRONICLE, December 16, 1994


Accessible Rights-of-Way: Sidewalks, street crossings, other pedestrian facilities, U.S. Architectural and Transportation Barriers Compliance Board, U.S. Access Board, November 1999.

“All Vehicle VOC and NOX Emission Factors by Speed, Summer and Winter,” graph provided by Ron Severence, Maine Department of Environmental Protection, 1997

An Analysis of Leadership, Politics and Ethics in the Stevens Avenue Traffic Calming Project, Part III, Ethics in the Stevens Avenue Project” by Scott Landry, Scot Mattox, Sara & Celeste Vigor, May 14, 1998 (Graduate paper for Muskie Institute at University of Maine Law School)

Boulder Fire Department Master Plan, Kevin Klein for City of Boulder CO, 1996

Building a True Community Final Report, Public Rights-of-Way Access Advisory Committee, U.S. Access Board, January 10, 2001

Deaths Expected from Delayed Emergency Response Due to Neighborhood Traffic Mitigation, Ronald R. Bowman, April 3, 1997

An Evaluation of the Speed Hump Program in the City of Berkeley, October 1997 (Damage to vehicles, impact on ambulance and fire services and people with disabilities.)

Guidelines for the Design and Application of Speed Humps, Institute of Transportation Engineers, 1997

The Impacts of Traffic Calming Measures on Vehicle Exhaust Emissions, United Kingdom,Transport Research Laboratory Report 482, PG Boulter, AJ Hickman

“Motor-Vehicle-Related Deaths Involving Intoxicated Pedestrians” – United States, 1982-1992,” Morbidity and Mortality Weekly Report, Vol. 43 / No. 14

911 Emergency Gate Review, Fire Chief Les Tyra, City of Houston Fire Department, November 17, 1998

Possible Neighborhood Traffic Calming Methods, Report to city council of Sunnyvale, CA, February 4, 1997 (Potential liability.)

Speed Hump/UC Plan Presentation Outline, draft report, Susan Sanderson, Transportation Planner, City of Berkeley, (Emergency response concerns from proliferation of speed humps. Humps not the tool felt they were.) 1995.

Sudden Cardiac Arrest, The American Heart Association, 1996

A Survey of Traffic Calming Practices in the United States, Institute of Urban and Regional Development by Asha Weinstein and Elizabeth Deakin, University of California at Berkeley, March 1998, (Conflict in neighborhoods.)

Stevens Avenue Traffic Calming Project, DeLuca-Hoffman Associates Inc., May 27, 1998, Portland, Maine (Increased accidents and pollution from traffic calming project.)

Traffic Calming: State of the Practice, Reid Ewing, ITE/FHWA, 1999

Traffic Calming and vehicle emissions: A literature review, Transport Research Laboratory Report 307, United Kingdom, P. G. Boulter and D. C. Webster, 1997


Americans with Disabilities Act, Title II, State and Local Government, Justice regulations, 28 CFR, 35.151, “New construction and alterations.”

Clean Air Act, EPA, Title 1, Part A, Air Quality and Emission Limits, Sec. 113 Federal Limits

Manual on Uniform Traffic Control Devices, Millennium Edition, USDOT/FHWA, 2000

Traffic Safety Facts 2000, National Highway Traffic Safety Administration, USDOT


“An Analysis of Speed Hump Effects on Response Times,” City of Austin, TX Fire Department, January 20, 1999

“The Effects of Speed Humps and Traffic Circles on Responding Fire-Rescue Apparatus in Montgomery County, Maryland,” Montgomery County Fire and Rescue Commission, August 1997

The Influence of Traffic Calming Devices on Fire Vehicle Travel Times,” Portland Bureau of Fire, Rescue and Emergency Service, January 1996

Memorandum from Nels Tahti, Administrative Analyst, City of Roseville, CA Fire Department (Time trials on streets with series of speed humps), June 4, 1991


Letter from Earl Noe, “I have disabled your car… because you have so little regard for laws,” THE BOULDER PLANET, October 9-15, 1996 (Opponent of devices has tires slashed.)

Letter from Karen Craig, Chair, Commission on Disability, Berkeley CA to Berkeley Mayor and City Council, November 10, 1998 (Problems of the disabled with vertical deflection devices.)

Letter from Special Transit of Boulder, CO to Boulder City Council, April 3, 1997 (Problems of disabled riders with vertical and horizontal deflection devices.)

Letter from Steven Beningo, Division Transportation Planner, USDOT, to Commissioner John Melrose, Maine DOT, August 13, 1998, (Rescinds funds for Portland’s traffic calming project because of increased emissions.)


Affidavit of Settlement for Permanent Disability for fire fighter, George Gosbee, Montgomery County, MD, 1998 (Settlement of $ 3,000 per month for life for injury sustained when hit speed hump traveling to scene of emergency.)

Appellant’s Brief in, Slager v. Duncan and Montgomery County MD to U.S. Court of Appeals, Fourth Circuit (Unpublished opinion, sets no precedent by rules of the court.)

Final Judgment, Twelfth Circuit Court of the State of Florida, June 29, 1998 (Judge Robert B. Bennet rules in favor of Windom and Hartenstine of Sarasota, FL)

Opinion of Attorney General, State of Maryland, No. 86-021, April 2, 1986 (Potential liability.)

Opinion of Thomas R. Powell, Senior Assistant City Attorney, The City of Wichita, KS April 1, 1986 (Potential liability.)


Housing Discrimination Complaint, filed by Calvin Hummer, President, Meadow Walk Town Home Association, Houston TX, May 28, 1997

“The Other Pine Intersections,” Ronald Bowman, 1996 (Graph showing increase in accidents at intersections with traffic circles on Pine St., Boulder CO.)

Program Application for CMAQ (Congestion Mitigation and Air Quality) funds from City of Portland, July 1994. (City agrees to remove temporary measures if CMAQ determines emissions are not lowered by project.)


“Traffic Calming Devices,” 1996, Portland Bureau of Fire, Rescue and Emergency Services, 55 SW Ash St., Portland, OR 97204