Cross Section Elements: Research and Synthesis of Practice

Abstract

Chapter 4, Cross Section Elements of TAC’s Geometric Design Guide for Canadian Roads (GDG) addresses design procedures and domains related to road cross sections (e.g. lane widths, special purpose lanes, shoulders, medians, outer separations and boulevards, curb and gutter and drainage), and presents typical cross sections as well as discussing considerations related to bridges, utility placement, snow storage and future widenings.

The 2017 update of TAC’s GDG did not incorporate major revisions to Chapter 4, which was previously updated in 2001. Volunteers on TAC’s Geometric Design Committee have completed a comprehensive review of the existing Chapter 4 and identified a number of sections that require updating, notably those pertaining to urban contexts. The working group also conducted a high-level survey of TAC member organizations that confirmed the need for both updated and new information in Chapter 4 to help respondents reduce their reliance on supplementary sources of design guidance.

This project represents the first phase of work needed to develop a new GDG Chapter 4, Cross Section Elements. A subsequent phase of work would be required to draft and finalize text, figures and tables for the new Chapter 4.

OBJECTIVES

The major objective of this project will be to research and synthesize current practices related to road cross section design in Canada, including those related to the following road elements:

• lane widths
• special purpose lanes including passing lanes, turning lanes, parking lanes, auxiliary lanes, weaving lanes, transit lanes, bicycle lanes, ramps and service/frontage lanes
• typical cross sections, including those serving multiple modes
• sidewalks, boulevards and border areas
• medians and outer separations
• shoulders
• curb and gutter
• surface drainage

Other issues to be addressed include:

• climate change considerations
• landscaping and streetscaping
• transit facilities
• loading and delivery zones
• curbside management (e.g. street furnishing, parking for shared bicycles/scooters, streetlighting)
• speed management measures
• safety devices
• buffer treatments (between different modes and uses)
• lateral clearance distance for railway signal assemblies
• low impact development
• complete streets (notably related to constricted areas, retrofits and bridges)
• accessibility and universal design
• intelligent transportation systems (ITS)
• design for future widening

The tasks included in this phase of the Chapter 4 update will include:

• a review of current practices and design standards within Canada and internationally
• a literature review of case studies and best practices for urban and rural cross sections
• consultation with road authority employees, consultants and academics (e.g. workshops)
• documentation of findings

The final deliverable of this project will be a research report documenting relevant practices and considerations related to cross section design for Canadian roads.