This memorandum report was prepared early in the study and is described in Section 2 of this report.
Pilot Test of Novel Speed Reducing Program
Contract No. DTNH22-99-D-05099, Task Order 2
October 11, 2000
SUPPLEMENTAL LITERATURE REVIEW
The purpose of this effort was to update the literature review performed for NHTSA's vehicle speed report (1). It was therefore initiated with a review of the speed report itself. Searches were then made of the Transportation Research Board Transportation Research Information Services (TRIS) database to identify studies published from 1998 to the present on the topics of traffic calming, speed, enforcement, education, and pedestrian safety. In addition, contact was made with selected NHTSA/FHWA representatives, with bicycle/pedestrian professionals, and with contributors to the vehicle speed report to request additional references and materials. Finally, Web sites of cities with known traffic calming programs were accessed to obtain additional reports and information.
In all, over 175 documents were identified and abstracts of each were read. Those for which hard copies were obtained and reviewed are listed at the end of this supplemental review. The subject matter of the reviewed documents ranged widely and included descriptions of specific traffic calming techniques, legal aspects of traffic calming, crime issues, property value issues, and others. Although all hard-copy documents that were received were read, the major interest was in identifying evaluative studies of methods of traffic calming, especially those involving education and enforcement. Very few evaluative studies were located. However, reports that summarized and quoted results of evaluative studies were found and proved useful.
The supplemental research information is based largely on two major documents that were produced since publication of NHTSA's speed report. One is the ITE report on the state of the practice of traffic calming (2). Among other topics, it provides a brief history of traffic calming, a toolbox of traffic calming measures, engineering and aesthetic issues, impacts of traffic management measures, legal authority and liability issues, warrants, project selection procedures, public involvement, traffic calming on other than neighborhood and collector streets, and traffic calming in new developments. Twenty United States traffic calming programs are featured in the document. Specifications proposed by certain jurisdictions or professional groups for selected measures are included. A second major input to the supplemental review is the FHWA synthesis of safety research related to speed and speed management (3). That report covers speed-safety relationships, factors influencing speed, speed limits and speeds, speed limits and safety, enforcement and engineering measures.
In the following paragraphs, brief summaries of the information included in the vehicle speed report are presented first and followed by any additional or confirming information obtained from the above two documents and from other materials identified in the supplemental review. A brief summary of the review is included at the end of this letter report along with a listing of the documents reviewed.
Vehicle speed report: NHTSA's vehicle speed report noted that speed humps can be successful in reducing both average and very high speeds and the result is often a reduction in crashes and crash severity. It noted the problem that humps affect different vehicles (e.g., trucks, buses, emergency vehicles) in different ways. Humps can be perceived as obstructions in the roadway. Roads that are narrower and less straight encourage lower speeds. Speeds through chicanes are reduced. Traffic islands and roundabouts also reduce vehicle speeds and have been shown to improve safety.
Supplementary Information: Additional or confirming information obtained on specific types of engineering traffic calming measures follows.
The ITE (2) report included speed, volume and crash data for many before and after studies in which various traffic calming techniques were used. ITE reported that speed humps have the greatest impact on 85 th percentile speeds of all traffic calming measures tested. Raised intersections, long speed tables and circles have the least impact. It reported that an international survey showed that traffic circles and chicanes had the most favorable impacts on safety. Although there are complaints about noise, traffic calming measures actually reduce noise levels. There have been legal threats, lawsuits and damage claims against communities for traffic calming and some jurisdictions have banned them.
FHWA (3) reported that the most effective traffic calming measures involve vertical shifts in the roadway. However, effectiveness is dependent on spacing. Greater reductions in speeds and crashes occur when combinations of measures are implemented systematically over an area wider than a single neighborhood.
The State of Delaware Department of Transportation (59) has produced a traffic calming design manual that provides guidance to state engineers regarding the appropriate use, design, and signing and marking of physical traffic calming measures. It does not cover measures that may improve street appearance (for example, planting streets on the roadway), nor does it cover education and enforcement measures. The manual outlines the procedural steps involved in effecting traffic calming in Delaware including a priority rating system. It describes appropriate volume and speed control measures, provides design guidance for each, and provides guidance on appropriate signing and marking for traffic calming measures
The City of Portland (24) reported that installation of 14-foot speed humps reduced 85 th percentile speeds by 6.9 mph to 25.8 mph, and speeds were not increased on parallel untreated streets. Twenty-two foot humps reduced 85 th percentile speeds by 8.2 mph to 29.9 mph. Traffic was often diverted to collector streets and arterials. Twenty percent of the motorists traveled greater than 25 mph after installation compared to 60 percent of motorists traveling above that speed prior to installation. Reductions in frequency were due largely to reductions in volume. Crashes were reduced 39 percent from 1.39 to 0.85 per year. Crash frequency increased on parallel streets. The crash rate was reduced 5 percent . Injury crashes were reduced 46 percent (a statistically significant reduction).
The City of Portland (45) joined forces with Recycled Technology in the development of a rubber speed hump. It was designed for use on streets with frequent maintenance needs – it can be easily removed for street resurfacing, worn sections can be removed and replaced, inlaid markings are possible. It also has temporary uses, e.g., to slow vehicles in construction zones or near street fairs where there is high pedestrian activity. It is comparable in effectiveness to the asphalt hump.
The City of Portland (46) tested split 22-foot speed humps spaced 28 feet apart for their effect on emergency vehicles. They created a chicane effect that emergency vehicles could pass around. The split humps were effective in slowing speeds on the roadway without delay to emergency vehicles. The spacing between humps did not seem to influence driver behavior. Especially on high volume streets, drivers showed no tendency to cross over the center line to avoid the hump.
San Antonio (22) achieved an average speed reduction of 12 mph at the hump and 7 mph between pairs of humps on the 10 streets on which 12-foot speed humps were installed. From questionnaires distributed to residents of the streets involved, the worst features of the humps were reported to be that they were noisy (19%), that the height was too low (18%) and that there were too few humps (11%). The best features were that they reduced speed (67%) and made streets safer (5%).
In NHTSA's national survey (20), 78 percent of the respondents reported that “road design changes/speed bumps” were very or somewhat effective in reducing speeding but only 63 percent approved of road changes to reduce speeding.
In a summary report, San Francisco, California, (49) stated that the city had generally positive experiences with chokers, medians, and traffic circles while experiences with speed bumps, diverters, and street closures were less positive. The bumps jolted cars and bicyclists, and the city stopped installing them. The city has installed a few speed humps but there are concerns about proliferation, emergency vehicle delay and traffic diversion. The city's experience with chokers didn't result in much of a speed reduction. Their experience with traffic circles has been limited but fairly successful. No data were given.
In a pilot program, the City of San Leandro , California , (26) installed speed humps on five of six parallel neighborhood streets and traffic circles on five of the six streets. One street did not receive a hump and one did not receive a circle. Results were that noise increased, steeper humps (3 inches versus 2.5 inches) were considered better, residents and pedestrians did not like the traffic circles although they reduced speed by an average of 7 mph, no differences in vehicle volume were noted, residents who wanted the humps didn't want them “in my backyard,” speed complaints on other streets increased when word got around about the speed humps, and a citywide policy is needed before traffic calming measures are installed.
In a series of case studies (31), it was shown that several jurisdictions have received complaints about traffic calming measures, particularly speed humps. Resentment is almost nonexistent on humps of height less than three inches. Some overly aggressive programs have resulted in a single lane for two-way traffic.
In a survey (28) of agencies using traffic calming measures, speed humps were the most widely used and elicited mixed reactions – some used them successfully, some used them initially and then had them removed, some had policies against them. There were no reported crashes or litigation on use of the device. Street closures caused problems including emergency vehicle access, segregation of communities, minor crashes and litigation. There were no reported safety or legal concerns with traffic circles, diverters, and roundabouts. Gates were the least used of the devices.
A study of Watts and Seminole Profile speed humps (37) suggested variations in dimensions suitable for bus and non-bus routes having posted speeds of 30, 40, and 50 km/h.
Cambridge (7) created chicanes by shifting parking from one side of the street to the other. At a raised intersection and at a raised crosswalk, speeds were reduced and the number of drivers yielding to pedestrians tripled. In addition, Cambridge replaced a traffic light with curb extensions and a raised intersection because drivers were always trying to beat the light. Most residents found it a safety improvement.
Lakewood , Colorado , (8) changed a straight section of roadway. A bicycle lane was converted to a sidewalk. A series of medians and curbside islands were constructed to create a narrow serpentine alignment. Eighty-fifth percentile speeds were reduced. The project did not make the roadway any more or less safe.
ITE (2) reported crash data for various types of traffic calming measures. By far the most impressive data were reported for the City of Seattle which installed circles at 113 intersections. There were 185 intersection crashes in the calendar year before the circles were installed and 11 in the calendar year after installation – a 94-percent reduction. Crash data for circles installed in other jurisdictions involved eight intersections or fewer and were less impressive than the Seattle data and sometimes showed a crash gain after installation. Crash data were also reported for humps (12 feet) that were installed on 19 roads in Omaha , Nebraska , and 15 roads in Montgomery County , Maryland . Before and after data for Omaha showed a 33-percent increase (from 30 to 40) in crashes after installation of the humps. The data for Montgomery County showed a 40-percent reduction (from 15 to 9) in crashes after installation of the humps. Data for other jurisdictions and for one other traffic calming measure (22-foot tables) involved installations on five or fewer roads; some showed increases and some decreases in crashes.
After complaining about cut-through traffic, two Michigan (27) communities conducted a joint survey and learned that less than 7 percent of the traffic was cut-through traffic. They then decided not to institute any traffic calming measures. The author states that when citizens complain, the response is sometimes a placebo (e.g., stop signs, speed humps or bumps, or “changes in road geometry to make the road less safe, so motorists will reduce speed”).
In New Mexico (29) the average speed at a temporary mid-block island on a paved street was 25 mph and the 85 th percentile speed was 33 mph compared to 41 mph and 48 mph on the same street without the island. On an unpaved street with a mid-block island, the average speed was 18 mph and the 85 th percentile speed was 23 mph in comparison to 28 mph and 34 mph without the island. It was concluded that the islands were slowing speeds as effectively as the humps that were located on nearby streets.
Idaho (30) reported on a three-year effort to plan for speed control in Boise subdivision designs. The proposed street width was 29 feet but, since homeowners were concerned about narrow streets, developers usually used 32 feet as the width. The local traffic calming program called for road humps a minimum of 600 feet apart. With that as the goal for a maximum sight distance, the desired street curve radius was set at 350 feet. Chokers creating a 28 foot street width had no effect on speed. Restrictions down to 20 feet were required before any appreciable speed reduction was noted. Chokers caused problems for larger vehicles, improved visibility for drivers and pedestrians, and decreased pedestrian crossing time. A revised plan relocated chokers to mid-block locations which reduced speeds without impacting corner turning radii. Median islands had similar impacts. Limited data available on block length show minimal speed differences for long and short block lengths.
A summary of traffic calming support provided to a region of Connecticut (32) involved identification of “best practices” in traffic calming, conduct of workshops involving citizens and public officials, and interviews with available local staff. Three case studies were analyzed and a final report was prepared that included a toolbox on traffic calming. The effort also involved development of a traffic calming ordinance.
The Victoria Transportation Policy Institute (23) referenced articles in the Journal of Visual Impairment and Blindness that noted that some traffic calming measures may cause problems for blind people. These include raised crosswalks when there is no detectable warning and neckdowns. The journal also noted that roundabouts may be more difficult for the blind because traffic is not straight and there are no regular breaks in traffic flow.
The Local Government Commission Center for Livable Communities (58) is preparing a summary of the effects of various traffic calming techniques on emergency response times. Solutions are proposed. Those techniques reported to cause minimal or no delay are speed pillows, medians, and landscaping. Speed humps cause an average delay of 6 to 11 seconds.
Roadway Perceptual Features
Vehicle speed report: The NHTSA speed report did not cover perceptual features of the roadway except for a study on use of transverse lines which showed that speeds were reduced initially, but the effects wore off in three weeks.
Supplementary Information: Additional or confirming information on these perceptual features follows.
ITE (2) reported that results from Howard County, Maryland; Beaverton , Oregon ; and San Antonio , Texas , have shown that vehicle speeds are as likely to increase as decrease with centerline or edgeline striping. However, the report noted that, even with the decreased widths, “pavement and lane widths remained substantial.” Speeds were unaffected in Orlando , Florida , where widths were taken down to nine feet. Portland , Oregon , used them in combination with other physical measures (speed humps and chokers) and got good results. Portland created a bicycle lane.
The Victoria Transport Policy Institute (23) reported that a study of 20,000 residential-area automobile crashes found that annual crashes per mile increased as street width increased beyond 24 feet between curbs, particularly on straight streets with low traffic volumes where average traffic speeds tend to be highest. Crash rates were approximately 18 times higher on a 48-foot wide street than a 24-foot wide street.
Smithfield (RI) (60) reported having two-way two-lane rural roads varying in width from 18 to 22 feet with neither curbs nor berms and open shoulders. The roads were often used as shortcuts, and speeding was common as motorists “hugged the middle.” When double yellow centerlines were painted on the roads, motorists were forced to stay right of center and speeding was reduced. No data were given.
In a survey (28) of agencies using traffic calming measures, street narrowing had the most response of all the measures as a device to cause potential crashes and cause the most concern from legal departments.
ITE (2) reported that Eugene , Oregon , had a 5-percent speed reduction with transverse markings placed before a horizontal curve. Howard County, Maryland, had a 12-percent speed reduction with transverse markings.
ITE (2) reported that building setbacks seem to reduce speeds. It noted that street trees may or may not have the same effect.
ITE (2) presented a comparison of subdivision street standards proposed for the Delaware Department of Transportation with AASHTO standards. The proposed standards were based on a design speed of 20 mph for local streets and 25 mph for residential collectors, a 266-inch school bus as the largest vehicle to be accommodated, and priority to be given to pedestrians over motor vehicles. Among others, it recommends lower speeds and narrower road widths than those specified by AASHTO. The rationales for deviating from AASHTO standards are given.
Vehicle speed report: The vehicle speed report identified no studies that used education alone as a speed reduction measure. Education was usually included as a minor adjunct to enforcement efforts.
Supplementary Information: Additional or confirming information on education follows.
ITE (2) noted the existence of neighborhood safety campaigns that typically consisted of personalized letters or general flyers distributed to residents. However, it found no empirical evidence regarding their impact.
FHWA (3) reported that a large proportion of studies mentioned some form of public information and education (PI&E). None attributed a significant reduction in speed, speeding, crashes or crash severity to any campaign that was not closely tied to an enforcement or engineering program. PI&E campaigns that accompany law enforcement programs increase positive public impressions toward police and result in safer driving habits.
It should be noted that cities that have established traffic calming programs, for example, Portland , Oregon , require neighborhood approval of a project prior to its initiation and involve residents in the planning process through neighborhood meetings and workshops.
The Safe Roads program (33) is a community traffic safety program in Massachusetts that is concerned with addressing the education and enforcement needs of speed management and transportation safety in general. A citizen speed watch pilot program was initiated on two streets. The program started with a one-month period of education in which citizens reported speeders' license plates and the location of speeding via a dedicated phone line. Law enforcement personnel reviewed each message and sent informational letters to the vehicle owners including a pamphlet on the safety risks of speeding. A loaner program of speed monitoring equipment was included as part of the citizen watch program as were increased law enforcement patrols. Before and after data showed average speed reductions of one and two mph on the two streets, 85 th percentile reductions of 5 mph on both streets, and reductions in those exceeding the speed limit of 3.8 percent and 14.1 percent . Reductions in operating speeds were noted nearly three months after the educational campaign. The Safe Roads program (51) continued in the summer of 2000 in three additional communities in Western Massachusetts . Each community was provided with radar equipment and speed boards. Letters regarding the safety aspects of speeding were written by the police to owners of speeding vehicles. Communities erected signs regarding the program (e.g., entering speed zone, radar in use). The program at one of the three communities is still ongoing and data have not yet been analyzed for the three programs.
Boulder , Colorado , (50) has a Neighborhood Traffic Mitigation Program that is initiated with a neighborhood education program. It provides a variety of materials including information for a newsletter, information on how to run a speed watch program, and a neighborhood speed pledge. If speeds are not reduced, enforcement is the second step. Data on the education program were not reported.
ITE (2) reported that, in general, neighborhood speed watch programs have not been effective because speed reductions are small and residents lose interest. A program in Gwinnett County, Georgia – in which data were collected by transportation department personnel, the offending residents were visited personally, names of offenders were published in a neighborhood newsletter, and offenders' memberships in a swim and tennis club were suspended – resulted in a reduction in 85 th percentile speeds from 45 mph to 35 mph. The program was labor intensive and fell victim to budget cuts. Tempe , Arizona , (47) and Tampa , Florida , (48) reported the existence of such programs.
In NHTSA's national survey (20), “increased public awareness of risks” was ranked by 72 percent of the respondents as very or somewhat effective in reducing speeding. In addition, 83 percent of the respondents strongly or somewhat approved of implementing this countermeasure to reduce speeding although only 40 percent felt it had some or a lot of effect on their driving.
In NHTSA's national survey (20), only 52 percent of the respondents felt that encouraging citizens to report drivers was effective in reducing speeding. It received the lowest ranking of any of the countermeasures investigated in the survey. Fifty-seven percent strongly or somewhat approved of the countermeasure as a means of reducing speeding.
Vehicle speed report: The vehicle speed report discussed enforcement studies that involved police presence at specific points (with and without actual enforcement) and use of a variety of equipments including photo radar, radar and laser detectors, speed display boards, vehicle-activated speed reminder signs, and school warning signs. In general, all methods of enforcement were effective in reducing speeds at the time and place they were used, but speed reductions decreased when enforcement stopped. The speed report concluded that enforcement was most practical on high volume roadways and at specific sites (e.g., schools).
Supplementary Information: Additional or confirming information obtained on specific types of enforcement follows.
ITE (2) stated that targeted police enforcement is impractical and expensive on low-volume streets. Boulder , Colorado , used targeted enforcement in four zones. No speed changes were noted in three targeted zones and speeds went up in a fourth.
FHWA (3) stated that compliance with speed limits is greatest in the vicinity of police vehicles and that aerial enforcement has a generally positive effect on reducing speeds.
An article on traffic issues in smaller communities (35) listed the following questions as issues that need reassessment: Is on-street parking associated with higher crash rates? Does on-street parking reduce mobility? Do we need to use one-way streets to move traffic efficiently in downtown areas? Are speeds on one-way streets hazardous to pedestrian movement? With the current cutback in traffic departments, what are alternative means of enforcement?
NHTSA (43) has prepared guidelines for developing a municipal speed enforcement program based on successful programs implemented in Modesto and San Bernadino , California . It makes the following suggestions, among others: select zones for study; deploy at hours of greatest risk, but vary the hours; use radar equipment (and laser speed measuring equipment if possible); use decoy vehicles at the enforcement sites and elsewhere in the community; and develop a public information and education program.
In NHTSA's national survey (20) “more police assigned to traffic” was ranked by 85 percent and “more frequent ticketing” by 82 percent of the respondents as very or somewhat effective in reducing speeding. These were the highest rankings received by any of the survey countermeasures. Seventy-three percent approved of adding police and 77 percent approved of more frequent ticketing as countermeasures to reduce speeding.
An abstract of a Michigan State study (21) showed that average speed on an interstate was reduced right before a police car's location but, after passing the patrol car, speeds increased to normal and occasionally higher than normal levels. In an overview of automated enforcement (34), the following were listed as important to successful automated enforcement programs: public education and awareness, involvement of the local judiciary, and passage of enabling legislation. The following current issues are discussed: privacy, distribution of ticket revenue, and ticketing procedures.
FHWA (3) reported on a study in which traffic enforcement notification signs were placed at either end of an enforcement zone and traffic laws were strictly enforced within the zone. In the study, officers handed out cards identifying the dangerous intersections targeted in the community and asking motorists to drive more safely. There was a 30-percent reduction in traffic violations during the enforcement period (3 years).
FHWA (3) reported that speed display boards have been shown to reduce speeds at the placement site.
ITE (2) noted that San Jose , California , found speed display boards to be effective only when displayed, and Kirkland , Washington , found a speed reduction of 6 percent after 30 days on streets with traffic volumes below 600 vehicles per day where most traffic is local and the displays raised the consciousness of local residents. On higher volume streets, the long-term effects were negligible.
ITE (2) stated that San Jose found that speed reductions obtained with photo radar seemed to hold up over time without enforcement and may have spread over into nearby untreated streets. Because of its expense, photo radar is most cost-effective if deployed on high volume streets.
FHWA (3) reported that foreign studies have shown significant reductions in crashes when photo radar is in use.
One paper on photo radar (25) reported that it was widely used throughout Europe and Australia and to a limited extent in North America to supplement police enforcement efforts. For example, in Victoria , Australia there was a 50-percent reduction in motorist triggering of the devices within three months of installation. Fatalities declined by 30 percent and the percentage of vehicles significantly exceeding the speed limit decreased from 20 percent to 4 percent.
The Insurance Institute for Highway Safety (IIHS) (42) reported that photo radar can be effective on busy urban interstates. Researchers in British Columbia analyzing a program using 30 cameras found a 7-percent decline in crashes, a 10-percent decline in daytime injuries, and up to 20 percent fewer deaths the first year the cameras were used. Speeding vehicles declined from 66 percent to fewer than 40 percent a year later.
Using cameras to enforce speeding was reported to be not politically acceptable in Phoenix (18). Boulder, Colorado , (50) found no statistically conclusive evidence that photo radar reduced speeding.
In NHTSA's national survey (20), 65 percent of the respondents reported having heard of photo enforcement devices. Seventy-five percent felt that photo enforcement would have some or a lot of effect on reducing speeding, and 71 percent thought it was a good idea to use photo enforcement for speeding. More women (78%) than men (63%) thought it was a good idea. The largest number of reasons given for feeling that photo enforcement was a bad idea (26%) was a concern over invasion of privacy, violation of rights, or government interference. Sixty-nine percent felt that photo enforcement was acceptable in school zones. Forty-three percent found it acceptable at sites where crashes are frequent, 36 percent at places where it is hazardous to stop, and 33 percent at places where stopping causes congestion.
FHWA (3) stated that laser guns were significantly more effective in identifying speeders than radar.
FHWA (3) reported that there was a slight reduction (of no practical use) in vehicle speed when drone radar was in use
Vehicle speed report: The vehicle speed report noted that changes in speed limits were found to change speeds significantly but by very small amounts. It also noted that a pavement marked with the word “Slow” and a large arrow placed before a sharp curve resulted in drops of mean speeds compared to nearby untreated curves. Other regulatory measures were not covered.
Supplementary Information: Additional or confirming information obtained on specific types of regulatory actions follows.
FHWA (3) reported several studies where there was little or no change in speeds from changes in speed limits. However, U.S. and foreign studies generally show an increase in speeds when speeds are raised on freeways. Crash incidence or crash severity generally declines when limits are lowered and rises when limits are raised, especially on freeways.
FHWA (44) analyzed speed and crash data collected from 22 States at 100 sites (rural, small urban, and urban) before and after speed limits were changed. Limits were lowered at 59 sites and raised at 41 sites. Data from 83 sites where speed limits were not altered were collected for comparison purposes. Results showed that neither raising nor lowering the speed limit had much effect on vehicle speeds. Mean and 85 th percentile speeds did not change more than 1 or 2 mph. The percent compliance improved when the speed limits were raised and decreased when they were lowered.
The Center for Livable Communities (15) noted that in many States the lowest speed that can be posted on a public street is 25 or 30 mph. In this regard, New York State law (19) has recently been changed to permit cities with populations larger than 1,000,000 to set speed limits as low as 15 mph on selected streets for the specific purpose of implementing physical traffic calming measures (not traffic signs only).
The Insurance Institute for Highway Safety (42) reported that London has a speed limit system on its M25 beltway that varies with traffic and speed conditions. Electronic loops detect traffic volumes and speeds and roadside processors analyze the data to detect where traffic is slowing. Speed limits ranging from 20 to 60 mph are posted on electronic signs. Enforcement is handled by cameras. There were 28 percent fewer crashes involving occupant injuries during the first year of the program, and vehicle-damage-only crashes went down 25 percent. Injury crashes on a comparison road without the new traffic control system increased 2 percent during the same time period.
A study (38) was conducted to determine a method of setting speed limits by considering pedestrians first. Pedestrian risk factors such as visibility, vehicle stopping distances, consequences of collisions, and their vulnerability by age groups were analyzed. Criteria for street-by-street analysis were developed consisting of land-use density, motor vehicle traffic volumes, presence of sidewalks and boulevards, and width of pavement. Organized into flow charts, the criteria provide target speeds for individual streets.
ITE (2) stated that most studies show little or no speed reductions mid-block with stop signs. There are problems with compliance.
Athens-Clarke County, Georgia, (14) compared speeds of two streets – one with all-way stop signs and one with speed humps. There was a very limited area of influence around stop signs before drivers increased speeds to a rate faster than before the stops were installed. Speeds decreased with speed humps.
ITE (2) stated that turn restrictions are popular with neighborhoods in Phoenix . They appear to be most effective at peak hours. Violations run around 50 percent without enforcement.
ITE (2) reported that no before and after data are available on the use of one-way streets as traffic calming measures. In a survey (28) of agencies using traffic calming measures, no safety or legal consequences were reported.
Boulder , Colorado , (50) tested a “rest on red” device at one intersection. This device remains red until it detects a vehicle traveling within the speed limit when it turns green to permit the vehicle to pass. “Speed Sensitive Signal” signs were posted to alert drivers that speeding would influence signal operation. Photo radar enforcement was used. Colorado did not report the data but indicated that vehicle speeds were not changed significantly. A possible explanation was that the combined volumes on the intersecting streets were too high for most of the day for the speed sensitive programming to influence signal operation. A test of “rest on green” signals was planned but not implemented because of limitations in the traffic signal controller software. Replacement software was reported to be under development.
The Virginia DOT (4) reported that the State has enacted a code that permits counties to install “Watch for Children” and “Additional $200 Fine” signs.
Hampton , Virginia , (10) implemented “invisible” traffic calming methods to reduce speeding and cut-through traffic. The methods included elimination of a left/through overlap causing delay for through vehicles, reduction of maximum green time for selected lights, prohibition of right turns on red, and changes in left turns from protective/permissive to protected only. Volumes and speeds dropped.
Pedestrian Crash Estimation
Vehicle speed report: The NHTSA vehicle speed report did not cover this topic.
Supplementary Information: Information obtained about pedestrian crash estimation follows.
Two papers were located that provided models for estimating pedestrian crash data. One paper (40) created a model to determine the probability of a pedestrian-vehicle collision since such collisions are rare on local streets. Both parametric and nonparametric methods are described, including an example in which estimates of the collision probability and the probability distribution of vehicle collision speeds are used to identify promising sites for traffic calming. The other paper (41) was used to evaluate the effect of roadway and area type features on injury severity of pedestrian crashes in rural Connecticut . Crashes were limited to those in which the pedestrian was trying to cross an uncontrolled two-lane highway. Variables that significantly influenced pedestrian severity were clear roadway (excludes on-street parking space), vehicle type, driver alcohol involvement, pedestrian age 65 or older, and pedestrian alcohol involvement. Speed limit was found to be a poor predictor as was average annual daily traffic, darkness, illumination, and weather.
The supplementary literature review revealed very little new information over that reported in NHTSA's vehicle speed report. Most of the information obtained served to confirm or amplify information contained in the NHTSA report. The points that may be of interest to the current speed study are listed below.
1. Literature Review on Vehicle Travel Speeds and Pedestrian Injuries (Leaf and Preusser). NHTSA Report No. HS 809 021, October 1999.
2. Traffic Calming: State of the Practice (Ewing). Institute of Transportation Engineers, Publication No. FHWA-RD-99-135, August 1999.
3. Synthesis of Safety Research Related to Speed and Speed Management (Stuster, Coffman, and Warren). Publication No. FHWA-RD-98-154, July 1998.
4. VDOT's Residential Traffic Management Program (Arnold and Cottrell). Paper presented at the Institute of Transportation annual meeting, August 2000.
5 Arterial Traffic Calming – Is It an Oxymoron? (West). Paper presented at the Institute of Transportation annual meeting, August 2000.
6. Balancing Mobility Needs and Community Issues Using Traffic Calming Techniques (Solarz, Jehanian, and Davis). Paper presented at the Institute of Transportation annual meeting, August 2000.
7. Cambridge 's Traffic Calming Program: Pedestrians are the Focus (Watkins). Paper presented at the Institute of Transportation annual meeting, August 2000.
8. Collector Street Traffic Calming: A Comprehensive Before - After (Buchholz, Baskett and Anderson). Paper presented at the Institute of Transportation annual meeting, August 2000.
9. Creating Walkable Communities: The Michigan Example (Sisiopiku). Paper presented at the Institute of Transportation annual meeting, August 2000.
10. Invisible Traffic Calming - Low Cost Solution Yielding Significant Benefits (Allsbrook). Paper presented at the Institute of Transportation annual meeting, August 2000.
11. The Legal Aspects of Traffic Calming - Negligence (Williams). Paper presented at the Institute of Transportation annual meeting, August 2000.
12. Lessons Learned to “Calm” a Traffic Calming Program (Zoumalan and Yalda). Paper presented at the Institute of Transportation annual meeting, August 2000.
13. Traffic Engineer Beware Traffic Calming Can Be Dangerous to Your Professional Health (Khorshid and Yalda). Paper presented at the Institute of Transportation annual meeting, August 2000.
14. All-Way Stops Versus Speed Humps: Which is More Effective at Slowing Traffic Speeds? (Clark). Paper presented at the Institute of Transportation annual meeting, August 2000.
15. Street Design Guidelines for Healthy Neighborhoods (Burden, Wallwork, Sides, Trias, and Rue). Center for Livable Communities, Sacramento , California , January 1999.
16. Streets and Sidewalks, People and Cars: The Citizen's Guide to Traffic Calming (Burden) . Center for Livable Communities, Sacramento , California , April 2000 .
17. Civilizing Traffic: The Manual - Neighborhood Traffic Calming in Honolulu (Burden). Walkable Communities, High Springs , Florida , May 1999.
18. Personal communication with Michael Cynecki, Phoenix , Arizona .
19. New York State Vehicle Code § 1642(a)26.
20. National Survey of Speeding and Other Unsafe Driving Actions: Volume I-Methodology, Volume II-Driver Attitudes and Behavior, Volume III-Countermeasures (Boyle, Dienstfrey, and Sothoron) NHTSA report Nos. DOT HS 808 748, 749, and 750, September 1998.
21. Effects of Police Presence in an Increased Speed Zone (Patel, Sisiopiku, and Taylor). ITE Journal , Vol. 68, No. 3, March 1998, p.12. (Abstract review only)
22. Speed Hump Effectiveness and Public Acceptance (Ballard). ITE Journal , Vol. 68, No. 2, February 1998, p.70. (Abstract review only)
23. Traffic Calming Benefits, Costs and Equity Impacts (Litman). Victoria Transport Policy Institute, December 1999.
24. City of Portland Speed Bump Peer Review (Robinson, Wempler, and Colyar). October 1998. (http://www.trans.ci.portland.or.us/traffic_management/trafficcalming/reports/reports.htm)
25. Automated Enforcement of Traffic Laws (Retting). TR News , Issue 201, March 1999, pp. 15-18, 29.
26. Growing Pains or Growing Calmer? Lessons Learned from a Pilot Traffic Calming Program avis and Lum). Paper presented at the Institute of Transportation International Conference , 1998.
27. Does Traffic Calming Make Streets Safer? (Beaubien). Paper presented at the Institute of Transportation International Conference , 1998.
28. Liabilities/Safety Issues with Traffic Calming Devices (Dabkowski). Paper presented at the Institute of Transportation International Conference , 1998.
29. Recruiting Private Help for a Public Demonstration Project: Taking the “Hump” out of Traffic Calming (Aspelin). Paper presented at the Institute of Transportation International Conference , 1998.
30. Designing Speed Controlled Subdivisions Without Road Humps (Szplett and Butzier). Paper presented at the Institute of Transportation International Conference , 1999.
31. Traffic Calming - Beware of the Backlash (Cline and Dabkowski). Paper presented at the Institute of Transportation International Conference , 1999.
32. A Traffic Calming Toolbox - A Technical Resource Developed for the South Western Region of Connecticut (Ford, Court, and Prosi). Paper presented at the Institute of Transportation International Conference , 1999.
33. The Effectiveness of a Community Traffic Safety Program (Blume, Noyce, and Sicinski). Paper presented at the Institute of Transportation : Transportation Operations Moving into the 21 st Century Conference, 2000.
34. Overview of Automated Enforcement in Transportation (Turner and Polk). ITE Journal , Vol. 68, No. 6, June 1998, pp 20-29.
35. Traffic issues for smaller communities (Edwards). ITE Journal , Vol. 68, No. 8, August 1998, pp.30-33.
36. Signs of things to come. Roads and Bridges , Vol. 38, No. 3, March 2000, pp. 60-65.
37. Towards a North American Geometric Design Standard for Speed Humps (Weber and Braaksma). ITE Journal , Vol 70, No. 1, January 2000, pp. 30-33.
38. Target Speeds for Speed Zoning and Traffic Calming in Residential Areas . Paper prepared for presentation at the Transportation Research Board's 80 th Annual Meeting, January 2001.
39. Making Walking and Cycling Safer: Lessons from Europe (Pucher and Dijkstra). Transportation Quarterly , Vol. 54, No. 3, Summer 2000.
40. Method for Estimating Effect of Traffic Calming Volume and Speed on Pedestrian Safety for Residential Streets (Davis). Transportation Research Record , Issue 1636, 1998, pp. 110-115.
41. Factors Influencing Injury Severity of Motor Vehicle-Crossing Pedestrian Crashes in Rural Connecticut (Zajac and Ivan). Paper prepared for presentation at the Transportation Research Board's 80 th Annual Meeting, January 2001.
42. Who Cares About a Camera If You Are Not Speeding? (Insurance Institute for Highway Safety) Status Report , Vol. 34, No. 6, June 19, 1999, pp.1-3.
43. Guidelines for Developing a Municipal Speed Enforcement Program (NHTSA) Undated. (http://www.nhtsa.dot.gov/people/injury/enforce/program.htm)
44. Effects of Raising and Lowering Speed Limits on Selected Roadway Sections (FHWA). November 1998. (http://www.tfhrc.gov/humanfac/rd97002.htm)
45. Rubber Speed Bumps (Portland , Oregon) (http://www.trans.ci.portland.or.us/traffic_management/trafficcalming/devices/)
46. Split Speed Bump (Mulder). January 1998 (http://www.trans.ci.portland.or.us/traffic_management/trafficcalming/reports/split.htm)
47. Speed Alert Program (Wakefield). June 15, 1999 (http://www.tempe.gov/traffic/speed.htm)
48. Tampa (FL) Neighborhood Speed Watch Program (http://www.ci,tampa,fl.us/deptpublicworks/transportation.htm)
49. Strategic Analysis Report on Traffic Calming (http://www.ci.sf.ca.us/sfta/final.htm)
50. Boulder (CO) Neighborhood Traffic Mitigation Program (http://www.ci.boulder.co.us/publicworks/depts/tr7.html)
51. Personal communication with Michael Blume, University of Massachusetts .
52. Speeders See the Light (Gilbert). Traffic Safety , January/February 1999, pp. 8-9.
53. An Economic Evaluation of Incremental Resources to Road Safety Programmes in New Zealand (Guria). Accident Analysis & Prevention , Vol 31, 1999, pp. 91-99.
54. Traffic Calming Primer (Pat Noyes & Associates). Boulder , Colorado , 1998.
55. Effective Traffic Calming Applications and Implementation (Saffel). Minnesota Local Road Research Board, Minnesota Department of Transportation, Office of Research Services, St. Paul, Minnesota, October 1998.
56. Practitioner's Forum: Video Technology in Traffic Engineering and Transportation Planning (Shuldiner). Journal of Transportation Engineering , May/June 1999, pp.169-175.
57. Managing Speed: Review of Current Practice for Setting and Enforcing Speed Limits . Transportation Research Board, National Research Council, Special Report No. 254, 1998.
58. Emergency Response: Healthy Streets and Traffic Calming (Burden). Local Government Commission Center for Livable Communities, Sacramento , California , planned publication date: November 2000.
59. Delaware State Department of Transportation Traffic Calming Design Manual . State of Delaware , Department of Transportation, Dover , Deleware, August 2000.
60. Rural Traffic Calming: Returning to Basics (Suzman). International Municipal Signal Association Journal , Volume 37, Issue 4, p.28.