But without occupancy/ridership figures and precise fuel consumption statistics (including the amortized energy expenditure used to build the train), it is not at all obvious that trains beat cars from a fuel-efficiency-per-passenger standpoint. Given the price tag on the train, it is not obvious that it is more efficient from a cost-efficiency-per-passenger standpoint either.
> (b) Much faster (SF -> LA in < 3 hours, versus ~6.5 for a car)
But the door-to-door time is what truly matters. You aren't factoring in travel time to and from the train station, or wait time at the stations.
> (c) Not subject to traffic (which can greatly increase the latter time)
As noted above, the first and last legs (involving getting to the train station) are subject to traffic. The train leg itself is subject to wait times as it won't be running 24/7 with a new train leaving every minute. In addition, there will likely be nontrivial TSA/VIPER security checkpoints that will further slow down travel.
http://motherjones.com/mojo/2011/06/tsa-swarms-8000-bus-
stations-public-transit-systems-yearly
Think you could avoid the TSA's body scanners and pat-
downs by taking Amtrak? Think again.
This is highly arguable. You can directly control the cleanliness/comfort/appearance of your own automobile, but you cannot control the cleanliness of public transport.
Moreover, you can leave items overnight in your car, play music without headphones, and have a full volume conversation on a hands-free headset (or with a passenger) without someone else overhearing. You can't do this on a train.