The development and testing of the roadside Inspection Selection System (ISS) have been in progress for more than 2 years. The ISS was developed as part of the Aspen roadside inspection software system in response to a 1995 congressional mandate calling for use of prior carrier safety data to guide in selection of commercial vehicles and drivers to undergo roadside inspections. The Aspen system includes software that helps conduct roadside inspections with portable microcomputers. Ten states were involved in the initial testing of the ISS, but a majority of states throughout the United States are now using the system. An analysis of almost 40,000 inspections conducted in 1996 revealed that the vehicle out-of-service (OOS) rate was 33.7 percent for those vehicles the ISS recommended for inspection versus 20.0 percent for those it did not. The driver OOS rate was 13.5 percent for those drivers recommended for inspection versus 9.9 percent for those not recommended. The ISS will thus help in targeting relatively unsafe carriers (as well as those for which there are insufficient data) and reduce the inspection burden on carriers proved to be safe. This means that more efficient use will be made of scarce resources by focusing on less safe vehicles and drivers. In addition, use of the ISS offers substantial benefits to society in safety and to safe motor carriers in cost savings. Presentations of the system and results of an evaluation survey completed by inspectors show the ISS to be well accepted by both inspectors and the motor carrier community.