Whether they realize it or not, travelers typically take into account three things when deciding on a mode of transportation: convenience, price and speed. Below I've included a chart comparing automobile and rail travel on some common routes, all of which, other than Washington, D.C.-to-Boston, are heavily subsidized by state governments. Other thoughts on the comparison:
Convenience: Traveling by train is convenient in that you can spend your time on a laptop, instead of honking at the guy who cut you off. Cars, however, provide for more privacy and you can leave or stop whenever you want.
Furthermore, the biggest advantage for the automobile is the mobility you enjoy once you arrive at your destination. If you're on a short business trip (or going to New York City), a train is probably fine, but otherwise constantly having to call a cab can be a big hassle. Once more trains come equipped with wireless Internet access, the balance might shift a little though.
More thoughts -- and the chart -- after the jump.
Price: This is where, surprisingly, trains have an edge, as you can see in the chart below. These driving prices are based on the federal reimbursement rate of 48.5 cents per mile, which has gone up quite a bit as gas prices have increased. Though not all employers follow the federal rate, the rail advantages are probably big enough that it's generally cheaper for a business to send someone by train than car.
One caveat is that these prices don't take into account the cost of getting to and from a train station (they also don't consider tolls on the roads or parking). If it's a $20 cab ride to the station, it might be just as cheap to drive.
Speed: Here's where the trains lose badly. The only routes where it's faster to take a train are Washington to Boston (on Acela Express) and Harrisburg to Philadelphia, which are the only two high-speed lines in the United States.
Many of the car travel times I list below are probably implausible during rush hour, but remember that often the trains arrive late too. Getting to and from the train station also takes time, whereas you can drive directly where you need to go.
Real high-speed rail would completely change this equation. For example, the bullet trains California envisions would travel at speeds up to 220 MPH and take riders from San Francisco to Los Angeles in less than two and a half hours. That isn't just less than half the driving time, it's also almost as fast as flying, assuming you show up for your flight at least an hour early.
However, California's project would cost $40 billion, which is why it will probably never happen, barring federal funding.
Route Car Time Rail Time Car Cost Rail Cost Washington, DC-Boston, MA 7:44 6:30 $213.40 $194.00 Harrisburg, PA-Philadelphia, PA 1:44 1:35 51.90 20.00 Milwaukee, WI-Chicago, IL 1:37 1:34 44.14 21.00 Raleigh, NC-Charlotte, NC 2:36 3:24 83.16 24.00 Oakland, CA-Sacramento, CA 1:17 2:00 39.29 18.00 Seattle, WA-Portland, OR 2:48 3:30 83.91 28.00 Chicago, IL-St. Louis, MO 4:52 5:30 144.05 22.00 Los Angeles CA-San Diego, CA 1:53 2:40 58.69 29.00