The following warrants for automated speed enforcement were published in 1993 by the Public Roads Administration in Norway:

• The mean traffic speed on the road section was greater than the posted speed.
• The road section had an accident density of at least 0.5 injury accidents per km of roadway.
• The accident rate on the road section was higher than the normal accident rate for that type of road.

It should be noted that automatic speed enforcement was implemented on many roadway segments up to five years before the warrants were published; therefore, from 1988-1992 many segments had automated speed enforcement even though they did not conform to all of the warrants published in 1993.

The road sections in this study ranged from 0.56 kilometers (km) to 20.0 km in length. The average "before" period was 3.94 years, and the average "after" period was 4.61 years. The data collection effort was completed by 1996.

As a result of limited “before” data related to vehicle speeds and property damage, the evaluation focused primarily on changes in accident rates.

RESULTS

After the deployment of automated speed enforcement the number of injury accidents declined by 20 percent. However, this reduction varied depending on whether the roadway segment met Norway’s warrants for deployment of automated speed enforcement.

• On roadway sections meeting the warrants injury accidents declined by 26 percent.
• On roadway sections not meeting the warrants injury accidents declined by 5 percent.

The author noted the findings in this study were limited. In general, the lack of speed data made it impossible to study the impact of automated speed enforcement on traffic speed, and the impact of traffic speed on accident rates. In addition, there were no data concerning the frequency and duration of system operations making it impossible to evaluate effects of "intensity of use" on changes in traffic speed and accidents. Also, driver behavior such as the "kangaroo effect," that causes drivers to slow down and then speed up after they pass a photo enforcement zone, was not investigated.