This report includes calendar years 1983 through 1989, and is the second speed survey made exclusively of rural interstate data. All data were retrieved from locations that have been exempted from the 55 MPH Speed Compliance Certification Program.

The results of this study show that all vehicles on all Indiana rural interstate highways, had an average speed of 65.6 mph in 1989. This is 1.6 mph higher than the 1988 average speed of 64.0 mph, and 1.7 mph higher than the average speed of 63.9 mph during the 1987 calendar year. In addition, comparing Statewide speed versus vehicle length during 1989 indicates that the average speed of cars was 66.6 mph. This survey also shows that short trucks (21-45 feet) had an average speed of 64.4 mph, and long trucks (46-99 feet) had an average speed of 63.3 mph. The final Statewide results also indicate that 85 percent of all types of vehicles on all rural interstate highways are traveling at, or less than 73.9 mph.

The charts, Figure 2 and Figure 3, graphically illustrate the speeds Statewide for all locations, and the percent greater than speed respectively. Table 5 summarizes an analysis of speed versus vehicle length Statewide during 1989, while Figure 5 graphically represents those results. Appendix A contains summarized statistics for each individual monitoring station from 1983 through 1989, while the Tables and Figures in Appendix B compare all stations. The Tables and Figures in Appendix C summarize the speed by length data at two stations that were used for comparing speed by length changes in 1989 from 1988. Summary Tables and Figures relative to speed versus length during 1989 can be found in Appendix D. Calculations for final Statewide statistics are located in Appendix E.

Report Number



traffic speed, trends, Indiana, interstate highways

Project Number


File Number


Performing Organization

Joint Highway Research Project

Publisher Place

West Lafayette, IN

Date of this Version