Development of Intrastate Inspection Selection System for Wisconsin

Roadside safety inspections have been an important component of federally supported programs to improve motor carrier safety. The inspection selection system (ISS) and its successor, ISS-2, were designed to help roadside inspectors target the vehicles of Interstate carriers with the worst past safety performance. ISS was used as a starting point for developing an intrastate ISS for Wisconsin. Logistics regression was used to identify the relevant independent variables. The logit model estimates the probability that a vehicle will be found to have an out-of-service (OOS) safety violation. An alternative to the logit model, a simple direct-estimation technique that uses the total OOS rate for a motor carrier, was found to produce the highest success rates in predicting inspections that result in an OOS violation. The model can be implemented as a field inspection tool and as a means to generate a list of intrastate carriers ranked by their historical OOS violation record.