Aside from expensive tunnel clearance issues, the other main problem is that much of the CORP is a 10 MPH railroad, with some short sections of 25 mixed in. While passenger trains could theoretically run a little faster, it would still take most of an entire day or more to run Medford-Eugene or Medford-Black Butte, CA with an average running speeds in the of 15-20 MPH range.

Aside from a few railfans, it would be nearly impossible for Amtrak to attract a sufficient base of passengers willing to travel 300 miles at such dismal speeds.

Upgrading 300 miles of CORP line to Amtrak-like speeds (generally 60 MPH or greater) would likely require expenditures on the order of hundred(s) of millions of dollars.