CHANGES IN SPEED AND SPEED ADAPTATION FOLLOWING INCREASE IN NATIONAL MAXIMUM SPEED LIMIT

This study replicates a 1985 study showing that drivers adapted to freeway speeds travel faster on roads connecting with the freeways than do other drivers on the same roads. In addition, the study indicates that travel speeds on these freeways were faster in 1988 even though they had retained the 55 mph (88 km/h) limit and were distant from highways authorized for the 65 mph (105 km/h) limits. These findings suggest that allowing higher speeds on some highways not only causes higher speeds on local, connecting roads through speed adaptation, but also may cause higher speeds on other, unconnected and distant roads through some indirect process of speed generalization.