Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Impact of Highway and Bridge Investment on Conditions and Performance

Transit Investment Impacts

Methods for Increasing Future Investment for Transportation Projects

Impact of Investment Levels on Different Types of Highway User Costs

The HERS model defines benefits as reductions in highway user costs, agency costs, and societal costs. Highway user benefits are defined as reductions in travel time costs, crashes, and vehicle operating costs. Chapter 7 defined a highway Maintain User Cost benchmark, indicating that an average annual investment of $53.9 billion would be required to maintain highway user costs at their baseline 1997 levels. The highway Maintain Travel Time benchmark, defined as the average annual investment required to maintain travel time costs at current levels, was projected to be $67.9 billion.

Exhibit 9-4 describes how travel time costs, vehicle operating costs and crash costs are influenced by the total amount invested in highways. The highway investment levels shown in the table line up with those in Exhibit 7-3, which defined the highway scenarios and benchmarks used in this report. Each row represents a different minimum BCR cutoff point in HERS, as discussed in Chapter 7. As in Exhibit 9-1, the italicized bridge values shown in the second column are interpolated or extrapolated from the two bridge investment requirement scenarios to facilitate comparisons with the combined highway and bridge spending projections from Chapter 8.

Exhibit 9-4. Projected Changes in Highway User Costs Compared to 1997 Levels
for Different Possible Funding Levels

As shown in Exhibit 9-4, while an average annual highway investment of $53.9 billion would maintain overall user costs, the effect on individual user cost components would vary. Travel time costs would rise 1.5 percent, while vehicle operating costs and crash costs would fall by 1.2 percent and 1.6 percent respectively. This indicates that at this investment level, HERS predicts that there would be a relatively greater rate of return on improvements aimed at reducing crashes rather than those aimed at reducing congestion.

The improvements recommended by HERS would reduce crash costs at all levels of investment shown in Exhibit 9-4. Vehicle operating costs would be maintained if average annual investment reached $46.9 billion for highways. Combined with projected bridge investment requirements (extrapolated from the two scenarios derived from BNIP), total highway and bridge investment of $52.2 billion would be required to maintain vehicle operating costs. This is above the $48.7 billion level of 1997 highway and bridge capital outlay, but below the $53.6 billion average annual capital outlay projected for 1998_2003 in Chapter 8. As indicated earlier, maintaining travel time costs would be significantly more expensive.

The percent change in user costs shown in Exhibit 9-4 are tempered by the operation of the elasticity features in HERS. The model assumes that if user costs are reduced on a section, additional travel will shift to that section. This additional traffic volume tends to offset some of the initial reduction in user costs. Conversely, if user costs increase on a highway segment, drivers will be diverted away to other routes, other modes, or will eliminate some trips entirely. When some vehicles abandon a given highway segment, the remaining drivers benefit in terms of reduced congestion delay, which offsets part of the initial increase in user costs.