The Regional Express Rail (RER) project is part of the Ontario provincial government's $C 15bn ($US 13bn) 10-year transit investment plan for the Toronto and Hamilton area and includes proposals to electrify Metrolinx-owned Go Transit commuter lines to offer 15-minute frequencies in core areas with stopping and semi-fast services to meet demand and reduce journey times.

At the heart of the plan is the SmartTrack proposal, which involves using the Kitchener and Stoufville lines to create a 53km 22-station east-west electrified corridor providing an express service across Toronto. The project could be completed within seven years using $C 2.5bn in funding from the city. SmartTrack would be delivered and operated by Metrolinx, using the Toronto Transit Commission (TTC) fare system.

Metrolinx says the preliminary business case for the RER project is positive and it has begun developing a public consultation strategy. In addition it says it will work closely with Canadian National (CN), Canadian Pacific (CP), and Via Rail to advance service expansion and electrification, particularly on lines owned by CN and CP.

Work is also being carried out to develop a service concept for each line, together with infrastructure requirements and a phasing plan to determine the priority corridors. Metrolinx expects to complete the service concept in the first quarter of next year.

With a more intensive two-way service, track-doubling and additional platforms will be needed on some lines and the project may also require grade-separated junctions and the elimination of level crossings at some locations. New stations are also being considered.

According to the preliminary business case, ridership on Go Transit could more than double from 200,000 per day to more than 450,000 by 2031 with the implementation of RER, while Go's share of trips of 10km or more could triple from 3.6% by 2041. Metrolinx says further work will now be carried out to define costs and benefits on a line-by-line basis.

A number of early actions have been identified to implement the RER project, and environmental assessments have already been completed on additional tracks on the Stoufville and Barrie Lines together with electrification of the Kitchener Line (including the Union-Pearson airport express service) and the Lakeshore West expansion. A number of other projects that support the RER plan are already underway such as the Union Station modernisation, while contracts have been awarded recently for the Union Station Corridor resignalling, which will be essential to increase capacity in the core of the network.