Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Summary

Road Conditions

Bridge Conditions

Transit System Conditions

Lane Width

Lane width affects capacity and safety. For example, narrow lanes prevent a road from operating at capacity. As with roadway alignment, lane width is more crucial on functional systems with the higher travel volumes. Currently, high-type facilities (e.g. Interstates) are expected to have 12-foot lanes. Exhibits 3-15 and 3-16 illustrate that over 99 percent of the all Interstate miles meet the 12-foot standard. The percentage of 12+ foot lane widths decreases as the travel volume decreases. This relationship is seen on urban collectors and major rural collectors which have 51 percent and 36.8 percent respectively of 12+ foot lanes. The lanes that are less than 9 feet are mainly concentrated on the collector roads.

Exhibit 3-15. Rural Lane Width, by Functional System, 1997

Exhibit 3-16. Urban Lane Width, by Functional System, 1997

Exhibit 3-17

12+ Foot Lanes, Rural and Urban, 1993 and 1997

Lanes have been widened over time through new construction, reconstruction, and widening projects. Since 1993, the rural mileage with lane width greater than or equal to 12 feet increased from 51.8 percent to 53.0 percent while the urban mileage with 12 foot+ lanes increased from 64.1 percent to 66.2 percent [see Exhibit 3-17].