Chapter 8: Mobility Corridor (5 R) Design Criteria

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Section 1: Overview

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Introduction

Mobility corridors are intended to generate, or produce anew, very long term transportation opportunities. These transportation opportunities may include multiple modes such as rail, utilities, freight and passenger characteristics. These modes may occur within a single corridor alignment or the modes may be separated for some intervals. This chapter is intended to provide design guidance on the roadway aspects of these mobility corridors. This guidance can be expected to be updated as additional experience in gained in the planning, design, construction and operations of these transportation facilities.

The primary focus of these corridors is mobility. The roadway portions of a mobility corridor facility are intended for long distance travel, and will therefore, be very controlled in terms of access. The access will be limited to public roadways via ramp connections. Access will not be allowed along these ramp connections.

Since these corridors are intended for mobility, the design speeds presented in this chapter are between 85 mph to 100 mph [130 to 160 km/h]. Because mobility corridors may be generated or regenerated, this design criteria may be applied when planning new facilities or reconstructing existing corridors. While higher operating speeds may not be appropriate in all instances (such as densely developed urban areas), these higher design speeds can be applied, and should be considered, whenever prudent.

With respect to facilities that one day could be part of a major corridor, particularly new location routes, it is strongly recommended that these facilities be initially designed to accommodate a 100 mph design speed. Even though the facility may initially be posted for an 85 mph speed, the higher design criteria will allow the greatest flexibility, both in the roadway portion as well as for other transportation modes within the right of way, in terms of maximizing the future use of the corridor.This does not mean that all projects should be over-designed. If, through the project development process it is determined that substantial, adverse and unavoidable social, economic and environmental impacts will occur, then different design criteria may be appropriate. Contact the Environmental Affairs Division and the Right of Way Division as questions arise about environmental and right of way impacts while planning for higher design speeds.

As always, the potential long-term use and growth of the system should be considered and appropriate planning and engineering principles should be applied. Again, these mobility corridors are not primarily intended for local travel.

Section 2 discusses the features and design criteria for the roadway portion of mobility corridors and includes the following subsections.

  • Lane Width and Number
  • Shoulders
  • Pavement Cross Slope
  • Vertical Clearances at Structures
  • Stopping Sight Distance
  • Grades
  • Curve Radii
  • Superelevation
  • Vertical Curves

Departures from these guidelines are governed in Design Exceptions, Design Waivers and Design Variances, Chapter 1.

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