Are you retarded? The US has the worlds most extensive freight rail system, passenger rail can share the same right of way as long as the scheduling is lined up, some minor upgrades to the signaling are implemented, and the tracks are doubled (as in, one track for one direction one track for another). Bare bones commuter rail systems sharing right of ways with freight would only cost $2-10 million per mile and most of the cost would just come from building stations which wouldn't need to take up that much space. The maximum speed that those trains can get to while on freight right of ways is usually between 60-80 mph which does beat cars once you account for traffic.
If you want to optimize for speed then you would place the tracks in the medians or to the side of highways since by law they have to have some space between it and whatever property is nearby. Most of the expense there would come from the train having having to go above grade at interchanges and them having to split off the right of way to go to whatever xyz union station it terminates at. Very little land acquisition would need to be done because both highway and freight rail projects have done it for them.
Both of these methods were used when the Brightline between Miami to Orlando was made making it only cost like $6 billion and it's route ridership is excepted to reach 8,000,000 this year which is comparable to what California HSR will get but for like 5% the cost.
Please understand that when I'm talking about passenger rail, I'm not talking about bullet trains, I'm talking about regular trains that go between 60-125 mph.
