the truth about photo radartopical discussion paperscontact SENSEtext map of SENSE web siteback to SENSE home page

The Myth of 'Speed Kills' and the Dangers of Slow Driving... 

Mike A. Winnett. "A Review of Speed Camera Operations in the UK." PTRC Paper, (1994), p. 268.
"It should not necessarily be assumed however that accidents are caused solely by drivers at the higher end of the speed distribution."

Samuel C. Tignor and Davey Warren. "Driver Speed Behavior on U.S. Streets and Highways." Institute of Transportation Engineers: 1990 Compendium of Technical Papers, 1990 August, p. 85.
"The accident involvement rates on streets and highways in urban areas was highest for the slowest 5 percent of traffic, lowest for traffic in the 30 to 95 percentile range and increased for the fastest 5 percent of traffic."

David L. Harkey, H. Douglas Robertson, and Scott E. Davis. "Assessment of Current Speed Zoning Criteria." Transportation Research Record, 1281 (1990), p. 51.
"In general, 85 percent compliance was achieved at speeds 10 mph [16 km/h] over the posted speed limit; ... Speed at which accident risk is minimized occurred at the 90th percentile of the travel speeds observed."

Photo radar in BC will target drivers starting at the 85th percentile -- drivers travelling in the 80th to 95th percentiles have the least accident involvements of all vehicles on the road.


Ezra Hauer. "Accidents, Overtaking and Speed Control." Accident Analysis and Prevention, 3 (1971), p. 7.
"...driver education, speed limits, 'speed-kills' - like publicity, etc. may create the impression that slow driving is safe driving."

"...the indiscriminate public crusade against speeding should be replaced by a balanced approach emphasizing the dangers of both fast and slow driving."

"... the imbalance in public attitude toward speed may create a false notion of safety at low speeds."

N. J. Garber and R. Gadiraju. "Factors Affecting Speed Variance and Its Influence on Accidents." Transportation Research Record, 1213 (1989), p. 69.
"... there is no strong correlation between accident rates and average speed for any given type of highway... This tends to support the theory that higher speeds do not necessarily result in higher accident rates."

Charles A. Lave. "Speeding, Coordination, and the 55 MPH Limit." The American Economic Review, 75.5 (1985 December), p. 1163.
"... all current safety campaigns emphasize that 'speed kills.' They imply that the slower driver is the virtuous one and is helping protect himself and other drivers. It isn't so. To reduce fatalities, it is important that everyone drive at about the same speed. Thus the major consideration in choosing a speed limit is that it be obeyed. And the major consideration for police is to reduce variation, not speed, because slow drivers are as much a public hazard as fast ones."

Ezra Hauer. "Accidents, Overtaking and Speed Control." Accident Analysis and Prevention, 3 (1971), p. 7.
"Driver education should bring to the driver's attention what his senses are incapable of telling him. Namely, that the risk to be involved in an accident is smallest in the vicinity of the median speed. 'Median speed driving' could be promoted also by advisory traffic signs."

"...a false notion of security induces some drivers into slow driving... the driver's intuition does not tell him that driving below the median speed increases his chances to be involved in accidents."

"The first question to be posed concerns the apparent irrationality of driving below the median speed. Seemingly, the slow driver accepts higher risks without any discernible reward (unlike the fast driver who is possibly trading safety for time savings). ... the accident severity argument can hardly be used as a valid excuse for slow driving."

Insurance Corporation of British Columbia, Traffic Safety Research Department, 1990. "Public Attitudes Towards the Use of Automatic Cameras for Enforcement of Traffic Law Infractions", p. 39:
"The issue seen as the greatest concern was slow drivers. Almost 85% of the drivers felt that slow drivers were occasionally, very frequently or always a problem. Almost 50% considered slow drivers as frequently or always a concern."

SENSE has called upon the Minister of Transportation and Highways to enact clear laws against impeding traffic.


Mike Kawczynski. "Speed-Flow Relationships on Rural Roads in British Columbia." Victoria, 1994. p.25:
"Passing lane[s] on level terrain induces much higher speeds than 4-lane highways. The 85th percentile speed is 22 km/h over the 90 km/h speed limit"

Probable Cause: Drivers who impede traffic on impassable sections of road tend to speed up when road and sight conditions improve. This makes it more difficult for other vehicles to successfully and safely pass the normally slow drivers.

Potential Solutions: Drivers should be taught to drive at consistent speeds, and to yield right-of-way to faster moving vehicles when they cannot maintain consistent speeds.

Ezra Hauer. "Accidents, Overtaking and Speed Control." Accident Analysis and Prevention, 3 (1971), p. 13.
"It has been shown, that both an upper and a lower speed limit reduce the number of overtakings... Surprisingly, the imposition of a lower speed limit is two to three times more effective in reducing overtakings that an equivalent upper speed limit."

Washington State Motor Vehicle Statutes, West's Annotated Version, section 46.61.425 (1).
"No person shall drive a motor vehicle at such a slow speed as to impede the normal and reasonable movement of traffic except when reduced speed in necessary for safe operation or in compliance with the law; Provided, That a person following a vehicle driving at less than the legal maximum speed and desiring to pass such vehicle may exceed the speed limit, subject to provisions of RCW 46.61.120 on highways having only one lane of traffic in each direction, at only such a speed and for only such a distance as is necessary to complete the pass with a reasonable margin of safety."

Implications: Slow drivers are in violation of the law, and other drivers may reasonably exceed the speed limit in order to safely pass the slow vehicle. British Columbia laws encourage slow driving, and penalize drivers if they ever exceed the speed limit for any reason.

Washington State Motor Vehicle Statutes, West's Annotated Version, section 46.61.427.
"On a two-lane highway where passing is unsafe because of traffic in the opposite direction or other conditions, a slow moving vehicle, behind which five or more vehicles are formed in a line, shall turn off the roadway wherever sufficient area for a safe turn-out exists, in order to permit the vehicles following to proceed. As used in this section a slow moving vehicle is on which is proceeding at a rate of speed less than the normal flow of traffic at the particular time and place."

Note: Interestingly this law refers to speed less than normal flow, not less than speed limit.

Implications: Enact this type of law in British Columbia, designate pull-outs, erect signage, and enforce it!


What happens when you slow down all the vehicles on the road (by continually telling drivers that speed kills)? - you increase volume! And what does volume lead to? - more accidents...

Siem Oppe, "The Development of Traffic and Traffic Safety in Six Developed Countries." Accident Analysis and Prevention, 23.5 (1991), p. 401.
"... a striking relation is found between the volume parameters and the fatality rate parameters, suggesting that the number of fatalities is a function ... of the amount of traffic..."

Lasse Fridstrøm and others, "Measuring the Contribution of Randomness, Exposure, Weather, and Daylight to the Variation in Road Accident Counts." Accident Analysis and Prevention, 27.1 (1995), p. 1.
"... it may seem unlikely that very substantial reductions in the accident toll can be achieved without a decrease in the one most important systematic determinant: the traffic volume."

 Rev: 1998.09.29 contact SENSEtext map of SENSE web siteback to SENSE home pageback to top of this page