Caltrans TOPS Evaluation: Assessing the Net Benefits of ITS Applications

Method

The purpose of the research was to provide the Caltrans Traffic Operations Group and New Technology Group with a measure of the expected net benefits with the application of ITS projects to parts of the California highway system. The value of the research is that it would provide measures of the changes in benefits from ITS projects as the size of the projects change and as projects are introduced in combination with one another.

The outcome of a set of experiments undertaken to assess the net benefits of ITS applications in a stylized urban and near-urban highway network is presented. The work was completed using the IDAS Build I package. Despite the limitations of this first generation package, the research was able to assess a number of different ITS technologies including ramp meters, incident management, integrated technologies and synergies from multiple ITS applications.

Findings

While not able to conduct the experiments originally envisioned and not having been able to utilize Paramics as the preferred simulation tool, the experiments conducted using IDAS were successful. They provided some insight into the application of ITS projects to a highway system. The research examined change in net benefits resulting from expansion of the number of ramp meters as well as a shift in technology from moving from pretimed ramp meters to centrally controlled ramp meters. The research also examined incident management and the change in net benefits as the response time to the incident was reduced. Finally, the research also examined the synergies that might arise as combinations of ITS applications are applied to the highway system.

The research concluded that there are diminishing returns to adding a given technology. With ramp meters, there was a huge transfer in benefits from arterial road users to freeway users since traffic was held on the ramp to increase speeds on the freeway by a small amount. However, when the model was shifted from 5 pre-timed to 5 centrally controlled ramp meters, an increase is seen in the benefit/cost ratio. The conclusion is that the shift from a pre-timed "old technology" ramp meter to a "central control" new technology results in considerable benefits. Furthermore, the benefits from new technology (i.e., ITS) exceed those of expanding the old technology (e.g., increasing the number of pre-timed ramp meters). The increase in benefits is sufficiently large that the "gainers" could compensate the "losers" and still be better off them selves.