The U.S. Department of transportation’s Federal Highway Administration review research on traffic speed.
The summary states:
- That the evidence shows that the risk of having a crash is increased both for vehicles traveling slower than the average speed, and for those traveling above the average speed.
- That the risk of being injured increases exponentially with speeds much faster than the median speed.
- That the severity of a crash depends on the vehicle speed change at impact.
- That there is limited evidence that suggests that lower speed limits result in lower speeds on a system wide basis.
- That most crashes related to speed involve speed too fast for the conditions.
- That more research is needed to determine the effectiveness of traffic calming.
Other statistics assert speeding (travelling too fast for the prevailing conditions or above the posted speed limit) is a factor in about 40 percent of road deaths. The RTA also say speeding increases the risk of a crash and its severity. On another webpage, the RTA qualify their claims by referring to one specific piece of research from 1997, and stating “research has shown that the risk of a crash causing death or injury increases rapidly, even with small increases above an appropriately set speed limit.”
The contributory factor report in the official British road casualty statistics show for 2006, that “exceeding speed limit” was a contributory factor in 5% of all casualty crashes (14% of all fatal crashes), and that “travelling too fast for conditions” was a contributory factor in 11% of all casualty crashes (18% of all fatal crashes).
