CARTEEH logo with green car and plant

Center for Advancing Research in Transportation Emissions, Energy, and Health (CARTEEH)

A USDOT University Transportation Center

Reduced Speed Limits

Reduced speed limit is a measurable indicator which can reveal the extent of traffic accidents and fatalities. Speeding on traffic roads increases the driver’s chances of losing control, often making speeding drivers swerve into oncoming traffic or nearby barriers, resulting in car crashes and fatalities. As a result, reduced speed limits serve as a solution to minimize the number of road accidents and fatalities.1,2

This indicator helps determine the effectiveness of the following objectives

  • Less Contamination
  • Less Emissions
  • Less Traffic Noise
  • Connectivity and Inclusion
  • Healthy Destinations
  • Less Traffic Violence
  • Active Transportation
  • Green Space

Data Collection

Data on speed limits can be collected from various sources, including police departments, traffic or highway authorities, or insurance companies. Police departments often use data on vehicle speeds to enforce speed limits and target areas for enforcement. This data can also be used to support prosecution in court cases. Highway authorities may use speed data to assess the safety of their roads and identify areas where accident rates are high. Insurance companies may use speed data to help set insurance rates and decide whether or not to insure a driver. Speed data can be collected in several ways, including using speed cameras, radar guns, and GPS devices. Speed cameras are often used in areas with a high risk of accidents, such as near school and construction zones. Police officers commonly use radar guns to monitor speeds and issue tickets. GPS devices can be used to track the speeds of vehicles over time, which can help analyze traffic patterns.3,4

Examples

IIHS says speed limit increases since 1993 responsible for 36,760 extra deaths

Research studies have shown that higher speed limits lead to more road accidents. In one study, the Insurance Institute for Highway Safety found that states that increased their speed limits saw a 3% rise in fatalities on interstates and freeways. The study also found that the number of fatal crashes involving speeding rose by 5%. Other studies have shown similar results. A study by the National Highway Traffic Safety Administration found that speed was a factor in nearly one-third of all fatal crashes in the United States. The study also found that speeding contributes to nearly half of all traffic fatalities in rural areas. The results of these studies show that higher speed limits and increased traffic volume can lead to more accidents.

https://www.traffictechnologytoday.com/news/safety/iihs-says-speed-limit-increases-since-1993-responsible-for-36760-extra-deaths.htm

1. Driving above the speed limit can cause tragic car accidents [Internet]. Hoganinjury.com. [cited 2022 Aug 12]. Available from: https://www.hoganinjury.com/driving-above-the-speed-limit-can-cause-tragic-car-accidents
2. Archer, J., Fotheringham, N., Symmons, M., Corben, B. The impact of lowered speed limits in urban and metropolitan areas. Monash University Accident Research Center, Victoria, Australia.
3. Measuring vehicle speed with radar [Internet]. Drivesmartbc.ca. [cited 2022 Aug 17]. Available from: https://www.drivesmartbc.ca/police/measuring-vehicle-speed-radar
4. Leduc, G. Road traffic data: Collection methods and applications. Working Papers on Energy, Transport and Climate Change. 2008 Nov; 1(55):1-55.