FRA strongly advocates crash standards for passenger and freight equipment and played a large role in the development of Acela. We might scoff but look what has happened to equuipment involved in recent wrecks in Japan, Germany and France/Luxemoburg.

Colorado Railcar has been working to carve out a niche withe their DMU's that meet US crash standards. You might also recall a flap a few years ago when the Talgo sets were being criticized for not meeting the standards - hence the presece of a locomotive or cab car on eithe end.

FRA is willing to entertain lighter weight (and less crash-resistant) vehicles as long as they do not share track with conventional equipment. Examples are a street car line in Baltimore or NJT's Camden line DMU. In both cases freigth trains do operate on the lines but there is "temporal" (time) separation between freight and passenger operations.

Should CalTrain move to electrify, they could use equipment similiar to the new METRA order or they could ban simultaneous freight operation (tough to do south of Santa Clara).