Geometric Design Of Chain-On/Chain-Off Areas A Roadside Facility Designed to Enhance Safety and Manage Risk On the Alberta North-South Trade Corridor

摘要

Geometric design guidelines for chain-on/chain-off roadside facilities are not found in designguides such as the, Alberta Infrastructure Highway Geometric Design Guide, the TransportationAssociation of Canada (TAC) Geometric Design Guide for Canadian Roads or the AASHTO apolicy on Geometric Design of Highways and Streets. In addition, signing and marking of chainon/chain-off facilities are not contained in the TAC Manual of Uniform Traffic Control Devices forCanada. While a few highway agencies in the United States and Canada have developed theirown specific guidelines, they are often modified and applied on a case by case basis.The purpose of this paper is to present geometric design guidelines for chain-on/chain-offfacilities. Also, presented are guidelines for the signing and marking of chain-on/chain-offfacilities. The main purpose of developing these guidelines is to enhance safety and managethe risk of highway operation on steep upgrades and downgrades.In developing these guidelines selected highway agencies in Canada and the United Stateswere contacted in order to obtain geometric guidelines and signing of chain-on/chain-offfacilities. In addition, regional supervisors for Alberta Infrastructure and maintenancecontractors were surveyed for their opinions concerning the need for chains on steep grades.Three classes of chain-on/chain-off facilities are presented which include determination of needand signing of the facility. Geometric design guidelines include cross-section, taper length, andparking areas. Signing guidelines are also presented. While the need for chain-on/chain-offroadside facilities are limited to highways in mountainous terrain or highway crossing steep rivervalleys in rolling terrain, they are an important geometric design feature and part of an overallrisk management strategy for highway agencies.