@@pacificostudios Not really. According to the FRA regulations 110 mph requires quad gates. 125 mph require slightly better, reinforced quad gates. Anything _above_ 125 mph does indeed require full grade separation. So 125 mph is completely doable without grade separations if you install the so-called "immovable barrier" quad gates. This is commonly done on railroads all over the world. In Germany, a ton of HSR lines use these types of reinforced quad gates instead of full grade separation. It works fine and would be a fantastic cheap upgrade path to near HSR speeds.
@@TohaBgood2 - You also need in-cab signaling and automatic train stop to go 124 MPH in the U.S. I'm not sure if PTC will satisfy that, but before PTC, railroads relied on wayside signaling without ATS.
@@chrisdacrisis4670 MDOTs plan is to extend 110mph speed limits to Dearborn. They can do this because own the track. The speed drops west of Porter because Amtrak doesn’t own the track. There is/was a proposal to build separate tracks from Porter to Chicago away from freight interference and allow for higher speeds.