Research Papers

The Safety Benefits of 2+1 Roads and their Feasibility in the Canadian Context

Filename cmrsc19_66.pdf
Filesize 145 KB
Version 1
Date added June 7, 2009
Downloaded 3 times/fois
Category 2009–CMRSC-XIX–Saskatoon
Tags Session 6A
Author/Auteur Mustapha Zayoun


The “2+1” road, first implemented in the early 90s, is an innovative infrastructure measure used in several European countries designed to reduce fatal head-on collisions by eliminating improper and inattentive overtaking attempts. They are three-lane roads marked in such a way that the central lane offers the two directions of traffic alternating opportunities for overtaking. Opposing lanes of travel are separated by either a flexible wire rope barrier, or by a double solid line. The primary benefits of 2+1 roads are the overall reduction in the incidence of fatal collisions and in the severity of collisions in comparison to the regular undivided highways. This is thought to be achieved largely by the reduction of driver frustration and a transfer of collisions from the fatal category to the minor injury category. Moreover, the 2+1 road has been known to greatly improve the operational level of service of a road. Canadian road infrastructure is in a position to greatly benefit from road conversion to the 2+1 format, especially those rural undivided roads with increased rates of fatal collisions. This new 2+1 road design addresses many targets that Canada has aimed for in the Road Safety Vision 2010. These sub-targets include:
1. A 40% decrease in the number of road users fatally or seriously injured on rural roadways (defined as two lane roads where the speed limit is 80 - 90 km/h)
2. A 20% decrease in the number of road users killed or seriously injured in crashes involving commercial vehicles.
The main objective of this study was to investigate safety and operational benefits of 2+1 roads and the feasibility of implementing them on Canadian roads. The research found that there are several ideal conditions that need to be present in order to justify the implementation of a 2+1 road. These include high traffic volume (low level of service), minimum 6 km stretches of road with a limited number of intersections, and no bridges. Alberta conducted a feasibility study on 2+1 roads and came to the conclusion that since the majority of Alberta roads are already at a very high level of service with free flow conditions, and have several intersections, it would not be practical to implement the 2+1 road. Although it is not feasible for Alberta to implement the full 2+1 road concept, they have implemented the use of adding a passing lane at different sections of a specific road.

The implementation of the 2+1 road in Canada would have a positive impact in areas where the ideal conditions are present. It is up to all of the jurisdictions in Canada to individually assess their roads and areas of high collision and implement the 2+1 road where it is feasible.

Mustapha Zayoun