A network-based approach for evaluating and ranking transportation roadway projects

The evaluation and subsequent ranking of transportation roadway projects has traditionally been based on localized performance criteria that do not consider how individual projects may impact the network as a whole. A novel approach for prioritizing projects using a spatially sensitive, network-based performance metric called The Network Trip Robustness (NTR) is demonstrated in this paper. The NTR incorporates spatial aspects of network topology, network connectivity, and the dynamic rerouting of traffic on roadway links into the prioritization process. The approach is illustrated in practice using the actual road network, travel demand data, and roadway projects from the Chittenden County Regional Planning Commission (CCRPC) of Vermont. Results are discussed in the context of which projects provide the greatest expected travel time benefits for the network as a whole. Implementing more projects does not necessarily result in additional benefits, and the benefits associated with individual projects cannot simply be extrapolated across groups of projects in an additive manner. The evaluation of project groups appears to require a permutation-based approach where sequencing is critically important. The results can be generalized to other road networks and illustrate the spatially complex characteristics of transportation networks and some of the difficulties these characteristics create with respect to prioritizing roadway projects.

► There is a need for system-based transportation project evaluation criteria.
► More projects do not necessarily lead to more benefits and benefits are not additive across projects.
► Certain combinations of projects may reduce or even completely erase the benefits associated with individual projects.
► Sequencing projects is critically important and a permutation-based approach is needed for implementing groups of projects.