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21st Century Operations Using 21st Century Technologies

Use of Freeway Shoulders for Travel — Guide for Planning, Evaluating, and Designing Part-Time Shoulder Use as a Traffic Management Strategy


Part-time shoulder use is a transportation system management and operation (TSM&O) strategy that allows use of the left or right shoulders as travel lanes during some, but not all, hours of the day. Use of the shoulder is typically restricted to certain classes of vehicles. It is one possible strategy for addressing congestion and reliability issues within the transportation system, and can be particularly cost-effective where other alternatives to add lanes are infeasible or cost-prohibitive. In such situations, TSM&O alternatives, including part-time shoulder use, may be most appropriate for cost-effectively reducing delays and improving travel-time reliability. Part-time shoulder use is most cost-effective in constrained right-of-way conditions; however, there are certain minimum geometric clearances, visibility, and pavement requirements that must be considered before part-time shoulder use can be implemented.

Purpose, Scope, and Target Audience

The purpose of this guide is to provide guidance for planning, designing, implementing, and operating part-time shoulder use. This guide provides guidance on factors that need to be considered in:

  • Deciding through a comprehensive Performance-Based Practical Design(PBPD) process if the part-time use of the shoulder is a viable alternative for meeting the current and projected goals of the region;
  • Determining the impacts and feasibility of implementing part-time shoulder use; and
  • Designing and operating part-time shoulder use to optimize safety and lane utilization.

This guidance does not address the “part-time” use of a shoulder in work zones during construction (e.g., as part of a lane shift or lane closure), nor does it include the permanent, full- time “conversion” of a shoulder into a travel lane. Full-time conversion of the shoulder constitutes the “permanent elimination” of the shoulder and needs to be addressed in that context. This guide does not address pedestrian and bicycle considerations because it is focused on freeway applications. Part-time shoulder use on other types of roadways in the U.S. has been limited to bus-only shoulder use on a handful of arterials, and this guide presents only limited arterial-specific considerations.

The target audience for this guide consists of State Department of Transportation (DOT), toll agency, and Metropolitan Planning Organization (MPO) planners and designers.

Organization of Guide

The guide is organized in the typical sequence of steps required to plan, design, implement, and operate part-time shoulder use. Part I of this guide addresses the planning steps for considering part-time shoulder use.

  • Chapter 1 introduces part-time shoulder use and shows images of various facilities with part-time shoulder use.
  • Chapter 2 provides planning considerations and screening criteria to help users assess if part-time shoulder use is feasible on a specific facility using a Performance Based Practical Design (PBPD) approach.

Part II of this guide provides guidance on how to analyze part-time shoulder use.

  • Chapter 3 offers guidance on conducting operations analysis, including reliability analysis, of part-time shoulder use.
  • Chapter 4 provides guidance on assessing the safety impacts of part-time shoulder use.
  • Chapter 5 presents guidance on assessing the environmental impacts of part-time shoulder use, including air quality and noise.
  • Chapter 6 provides guidance on conducting benefit-cost analysis and computing the life- cycle costs of part-time shoulder use.

Part III of this guide provides information on how to design, implement, and operate part-time shoulder use once a decision to use it has been made.

  • Chapter 7 identifies and describes the various design considerations for part-time shoulder use, including geometry, pavement, drainage, signing and marking, and ITS design.
  • Chapter 8 describes how the environmental approval process and the design exception process are handled for part-time shoulder use, how to coordinate with stakeholders such as emergency responders and maintenance personnel, and how to successfully conduct outreach to the general public prior to beginning part-time shoulder use.
  • Chapter 9 presents best practices for maintenance, incident management, and other day- to-day operational issues of part-time shoulder use.

The appendices provide example applications of the guidance, along with case studies of successful applications of part-time shoulder use in the United States.

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