This would be really great to help the MAX as the region grows. It deals with two problems. One is that the Steel Bridge is at capacity for trains crossing and would not survive an earthquake. The other is that MAX trains were built to be limited by the length of Portland city blocks. While financially prudent at the time, it has proven to be problematic as ridership has grown, COVID times aside. Putting the MAX train underground would allow it to run trains with much longer length.