This study evaluates the effectiveness of the New Jersey Garden State Parkway (GSP) Alternate Bus Routing (ABR) system, an Advanced Public Transportation System (APTS). The GSP ABR Field Operational Test (FOT), which was conducted on a small portion of the parkway, was mainly concerned with real-time routing of New Jersey Transit (NJT) IntroductionOne of the most efficient ways to understand and assess the effectiveness of Intelligent Transportation Systems (ITS) in improving the existing transportation system is through the implementation of FOTs. FOTs are projects aimed at deploying promising ITS technologies in relatively small-scale networks. Evaluation of these FOTs is an integral part of the overall tests, because the major goal for the limited deployment of ITS technologies is to assess the effectiveness of the deployed ITS technology and draw general conclusions that can be used to ensure success of future large-scale ITS deployment projects. Currently, most ITS FOTs deal with passenger vehicles and related infrastructure. However, public transportation can be equally impacted by the use of advanced technologies recently introduced in the context of ITS. To better understand possible effects of advanced ITS technologies on public transit, real-world field implementation of these technologies and subsequent evaluation of their effectiveness is needed.The GSP ABR FOT project is concerned with real-time routing of NJT buses to avoid congested highway stretches along the test corridor shown in Figure 1. This is similar to the real-time traffic diversion concept implemented by incident management crews to reroute traffic around the closed highway link as a result of a traffic accident (Ozbay and Kachroo 1999). In this project, however, the diversion recommendation is limited to participating NJT buses; the other vehicles are not given any diversion messages. Based on the diversion