Traffic Speed Report No. 121

This report documents the May-August 1987 study of free flow automobile and truck speeds on tangent, level and dry sections of rural interstate, rural four-lane, rural two-lane and urban interstate highways in Indiana. The results of this report show that all types of vehicles, on all types of Indiana highways, had an average free flow speed of 59.3 mph in 1987. This indicates an increase of 0.7 mph from 1986. If the two urban interstates are excluded, the average speed on all types of rural highways in Indiana becomes 59.1 mph in 1987. This also represents an increase of 0.7 mph from 1986. All types of vehicles on rural interstate highways had an average speed of 62.3 mph, which is up by 2.2 mph from 1986. This is not unexpected, due to the implementation of the 65 mph speed limit on Indiana rural interstate highways effective June 1, 1987.