Raise the Hammer

I think someone (may have been the Province, might have just been some individual/firm) looked into putting a railway line in the median of Highway 401 through Toronto a few years ago. Additionally, the Spadina subway line in Toronto (built 1978) is largely in the median of the Allen Expressway (formerly Spadina Expressway, hence the name of the line). The problem with railways paired with highways is that highways are generally not near trip destinations or origins. As a result, in order to be successful, a railway on or next to a highway must be very fast in order to make it worth people's time to go out of their way to get to it. A railway with stops at each interchange (typical urban spacing is about 2km) averages about 40 km/h*, nowhere near fast enough to offset the travel time to and from stations.

Where highways are more useful as potential railways is for longer-distance trips between cities. The median of a highway is pretty much the cheapest place to build high speed rail, because it avoids the two largest expenses: building bridges over the railway and leveling the ground. Unfortunately using the existing highway space limits train speeds because highways' curves are designed for only 110 - 120 km/h. Trains can take corners a bit faster than road vehicles because they are on rails and can be tilted at a higher angle, but we'd still be lucky to top 150 km/h. Railways beside of highways (think Missisauga Transitway) are less cost-saving, because they still represent entirely new construction (bridges, tunnels, grading etc.).

Here are a couple railways in the median of highways I can can think of:
- Metrolink San Bernadino line in the median of Interstate-10 (Los Angeles)
- Line 25N in the median of Autoroute 1 between Brussel and Antwerpen in Belgium

However, the potential for highway-based railways in the GTHA is fairly limited, because most of our highways already have parallel railways, almost all of which are owned by Metrolinx (GO Transit). Many of them also have line geometry as good or better than what we'd get from a railway in a highway. For example, the speed limit on the Lakeshore Line is already 153 km/h (95 mph), and on the Kitchener Line, upgrades through Toronto are increasing the speed limit from 130 km/h to 145 km/h.

*Based on the Yonge North subway line, which has 2km stop spacing.