Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Background

Current Conditions and Performance

Projected Conditions and Performance in 2007

Resources Needed to Maintain and Improve the Interstate System

Addressing Interstate System Needs

Highway Operational Performance

Chapter 4 includes data for several operational performance indicators. [See Exhibits 4-3, 4-5, 4-6, 47 and 4-9.] Daily Vehicle Miles of Travel (DVMT) per Lane-Mile is a basic measure of traffic density. Since 1993, rural Interstate DVMT per Lane-Mile has increased an average annual rate of 3.4 percent per year, from 3,530 to 4,952. Over the same period, urban Interstate DVMT per Lane-Mile has grown at an average annual rate of 2.0 percent, from 11,230 to 13,696.

The Volume/Service Flow (V/SF) ratio measures the volume of traffic using a highway during the peak hour and the theoretical capacity of the highway to accommodate traffic. Sections with a V/SF ratio above 0.80 are traditionally considered to be congested. In 1997, 53.3 percent of urban Interstate highways had a V/C ratio greater than or equal to 0.80, up from 52.6 percent in 1993.

Delay is another calculated measure of operational performance. In 1997, average delay on rural Interstates was 2.313 hours per 1000 vehicle miles traveled (VMT). Delay has been increasing on rural Interstates in recent years. Average delay on Interstates in small urban areas was 0.496 hours per 1000 VMT. In urbanized areas under 200,000 in population, average delay per 1000 VMT on Inter-states was 0.909 hours. In urbanized areas over 200,000 in population, delay was much higher, at 2.533 hours per 1000 VMT. Delay on urban interstates has fluctuated in recent years, but 1997 delay is smaller than delay calculated using 1993 data.