EVALUATION OF UNMANNED RADAR INSTALLATIONS

Abstract

The objective of this study was to evaluate the speed effects of unmanned installations I75 in northern Kentucky. Emphasis was placed the collection and analysis of speed-related data. In addition, a survey of detector usage was made and historical accident patterns were documented. The following types of data were collected and analyzed: 1) Automatic speed data, 2) Manual speed data, 3) Speed data for vehicles with and without detectors, 4) Speed data with and without the presence of active police enforcement, 5) Radar detector usage data, and 6) Accident data. Speed measures analyzed included mean speed, standard deviation (variance) in speed, percentages or numbers of vehicles exceeding specified speed levels, and 85th-percentile speed. Statistical tests were used to evaluate the effects of radar. Results indicate that unmanned was an effective means of reducing the number of vehicles traveling at excessive speeds the study section of I75. The daily reduction in number of vehicles exceeding the speed limit (55 mph) by 15 mph was determined to be approximately 900 at Florence. At Ft. Wright (where the speed limit was 50 mph for cars and 45 mph for trucks), the number exceeding the speed limit (50 mph) by 15 mph was approximately 350 vehicles per day. When comparing mean speeds with radar on and radar off, there was no statistical difference at Ft. Wright. At Florence, the mean speeds showed a statistically significant decrease with radar on. Results from the data collected manually did not reveal any significant differences when comparing mean speeds with radar on and radar off. Apparently the sampling periods were insufficient to identify differences that were shown at locations where automatic equipment was used to collect continuous data. Approximately 42% of the trucks and 11% of the cars were found to be equipped with detectors. The use of detectors had a significant effect vehicle speeds. With radar on the speeds of vehicles with detectors decreased significantly compared to the radar off speeds, while the speeds of vehicles without detectors were not affected. Accidents in the northbound direction of I75 between Ft. Mitchell and the Ohio River decreased in the one-year period after July 1986, as compared to the three-year period before. Data after July 1986 corresponded to the start of the truck diversion and original installations of the unmanned units.