Out with the new and in with the old

Improvements and expansions to rapid transit systems often focus on developing new infrastructure. However, when planning new rapid transit, there is an opportunity to make better use of existing unused or underused legacy infrastructure.

New infrastructure can face numerous high-level challenges including high capital costs, environmental impacts from new development, and potential political and public/stakeholder opposition. 

Instead of focusing rapid transit planning solely on new infrastructure, an alternate way forward is to consider how to integrate legacy infrastructure to realize strategic goals in a cost-effective manner.

Legacy infrastructure includes previously developed transport corridors that are no longer in use for passenger services, or only see limited functional use. These unused or underused corridors can be integrated into new rapid transit projects to realize a number of benefits. 

A key cost in developing new rapid transit is ensuring a separate right of way. Legacy corridors often exist in their own right of way, and can be used to provide a high frequency fully grade-separated service at a fraction of the cost of completely new infrastructure, such as a new tunnel or viaduct. 

These spaces were originally developed to serve transportation, so land acquisition can be a less onerous process. Additionally, developing a transit project within these may require less disruptive construction than developing rapid transit along other corridors, such as arterial roads. If the corridor runs through areas of high potential for redevelopment, legacy corridor development may also be a catalyst for urban intensification. 

However, legacy infrastructure is not always an ideal fit for project goals. Some old corridors were deliberately remote from communities, so integration of those communities with new transit service may prove difficult. Stations that are well connected to surrounding communities and activity centers are often key project goals, to ensure that new transit can maximize ridership and catalyze new development. Likewise, ensuring that feeder services connect to the corridor may be a challenge, as rail corridors do not often have strong integration with local roads, or lie adjacent to a highway with limited exits. Legacy corridors are also geographically fixed and may require high-cost tunnels or viaducts to integrate them within the broader transit system.

The potential of legacy infrastructure should be determined by assessing its ability to contribute to the project goals, its fit with the broader transit network and regional land use plans, and its integration potential with surrounding communities and activity centers.

There is a growing need for new rapid transit in many major metropolitan areas across North America to meet mobility requirements in a sustainable manner. A review of the role of legacy infrastructure may help regions find new opportunities to improve services and significantly reduce the cost of system development.