Evaluation of Speed Limits in Kentucky

Abstract

The objectives were to examine current criteria and procedures used for setting speed limits and to determine appropriate speed limits for various types of roads. The study involved a review of literature, collection and analysis of speed data, and collection and analysis of accident data. The speed data included moving speed data on various highway types and a comparison of speed data before and after speed limit changes. Accident data were collected at locations where speed limits were changed and also on sections of adjacent Interstates with different speed limits. The speed data indicate that a large percentage of vehicle speeds exceed posted speed limits, with the highest percentage being on urban Interstates and two-lane parkways. The speeds for trucks were slightly lower than for cars. A comparison of speed data at locations where speed limits were changed showed only slight differences. A comparison of accident rates at adjacent sections of Interstate where the speed limit was 88.6 km/hr (55 mph) and 104.7 km/hr (65 mph) did not find a substantial difference in the total, injury, or fatal accident rates. Except where legislatively mandated speed limits apply, the 85th-percentile speed should be used to establish speed limits. Maximum limits are given for various types of roadways. Different speed limits for cars and trucks are recommended for some roadways. An engineering study must be conducted before the speed limit should be changed for any specific section of roadway.