Traffic Speed Report No. 102

This report is another in the continuing study of speeds o vehicles on Indiana highways. Observations of spot speeds were on interstate, four-lane and two-lane highways throughout the state during the July-September 1978 quarter. Analysis of the speeds showed the overall average speed for all vehicles was 57.2 mph. The overall average speed for passenger cars and all trucks was 57.6 mph and 56.8 mph respectively. These overall average speeds were 0.8 mph less for passenger cars and 0.8 mph less for trucks than speeds found in the April-June 1978 study (Speed Report No. 105). This report is also the 1978 annual speed study of JHRP and is compared with similar studies made during the summer months for the last ten years. A very small increase in speeds was noted for two-lane highways while a very small decrease was evident on all other types of highways. Speeds of passenger cars, however, are significantly less on all classes of highway than speeds during the pre-55 mph limit years. On the other hand, speeds of heavy trucks in 1978 are almost the same as speeds of heavy trucks during the pre-55 mph limit years of 1968-1973.