This measuring system consisted of magnetic loop detectors connected via rented telephone lines to an IBM 1800 system. Fourteen locations on Indiana state route 37 were instrumented for this collection effort. Each vehicle which passed over a sensor location produced signals, which the computer received and stored, relating to velocity, length, headway, location, direction, and lane of travel. To seel how traffic reacts to the presence of a police vehicle, both stationary and moving police cars were introduced into the highway environment. A variety of stationary police vehicle set-ups was tested, including a radar vehicle, a vehicle in an arrest situation, and two police vehicles in a 'pack' configuration. Also sampled were civilian, and unmarked and marked police vehicles for the moving enforcement vehicle tests, 19 Indiana State Police VEhicles were equipped with low-power transmitters. Compatible receivers located at 12 sensor sites translated police vehicle passages into computer compatible signals. These signals were collated with the basic vehicle information to individually identify the police vehicle in permanent storage. Analysis of the data showed that both mean speed and percentage of speed violators were affected by the enforcement vehicles. In terms of absolute reductions in these measures, the immediate effects were more pronounced for the more-threatening, than for the less- threatening, stationary vehicle configurations. The appendix contains a discussion of the computer sensor system, a supplementary analysis of variance, tables, a list of references, data on selected speed distributions from the IRPS sensor systems, a sample IBM 1800 statistical analysis program printout, and Monroe county accident data. Forty tables of analytical data are also included.
Abstract