The most expensive and hard to acquire land for a new rail ROW will be in urban areas. Check out the freeway medians in those areas on a satellite view. They've already been used up.
Even when using them in rural areas, problems like existing bridges and geometry come into play.
>>1901035>You’ll still need bypasses for sectionsYes, and those will require extensive flyovers or tunneling to get over or under the road.
If there is ever a need to add tracks, you're completely SOL... should have acquired a proper ROW with enough space to handle a reasonable amount of expansion.
Ultimately people don't go to freeways, they are just a conduit for them to get somewhere else. Anyone who has used a highway median train station knows they're unpleasant, and will naturally be space constrained, have less than desirable pedestrian access, and accommodating buses and parking will be another problem to tackle.
I don't see any upside to using extant highway medians to lay rail lines, but I do see a lot of drawbacks. It's only practicable when either the rail ROW was already in place and the highway was built next to it, or if the road and rail lines were planned and built together. Why permanently hamstring a project with this approach instead of just doing it optimally in the first place? Either way, it's going to cost an obscene amount of money.
