Afterword: A View to the Future

The data and analyses presented in this report are based on tools and techniques that have been refined over time, evolving to reflect changing priorities and incorporating the latest relevant surface transportation research to the extent possible. At the same time, there is considerable room for improvement in our understanding of the physical conditions, operational performance, and investment requirements for the Nation's surface transportation infrastructure.

This Afterword is intended to discuss the gap between the current state of knowledge and the type of information that would be necessary and desirable to make significant leaps forward in the comprehensiveness of the C&P report analyses. In some cases, significant improvements to the analysis would have to be predicated on changes or improvements in data collection, recognizing that such changes would need to be balanced against the costs of collecting such data. This section also describes some ongoing research initiatives to bridge some of the knowledge gaps described.

Highway operational performance is currently modeled rather than measured, but advances in ITS technology might make it feasible to collect speed information directly. Improved data and modeling would assist analyses of highway and transit physical conditions, safety issues, and environmental impacts.

At its core, transportation investment involves balancing the demand for transportation services with the supply of those services. Areas in need of further exploration include the full social costs of adding capacity, the modeling of transportation demand, the impact of ITS on increasing effective capacity, linkages between financing mechanisms and investment requirements, and the impact of congestion pricing on bringing demand into closer balance with supply. Multimodal analysis, lifecycle cost analysis, and the impacts of investment on productivity also warrant further study.