Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Summary

Economics-Based Approach to Transportation Investments

Highway Investment Requirements

Bridge Investment Requirements

Combined Highway and Bridge Investment Requirements

Transit Investment Requirements

Multimodal Analysis

HERS, TERM, and BIAS all use a consistent approach for determining the value of travel time and the value of life, which are key variables in any economic analysis of transportation investment. However, while HERS, TERM, and BIAS all utilize benefit-cost analysis, their methods for imple-menting this analysis are very different. The highway, transit, and bridge models build off separate databases that are very different from one another. Each model makes use of the specific data available for its part of the transportation system, and addresses issues unique to each mode.

These three models have not yet evolved to the point where direct multimodal analysis would be possible. For example, HERS assumes that when lanes are added to a highway, this causes highway user costs to fall, resulting in additional highway travel. Some of this would be newly generated travel; some would be the result of travel shifting from transit to highways. However, HERS does not distinguish between these different sources of additional highway travel. At present, there is no direct way to analyze the impact that a given level of highway investment would have on transit investment requirements. As HERS, TERM, and BIAS continue to evolve, it should become easier to integrate their separate approaches.