Multitasking is good.....
The Economist.com has a blog post talking about the one successful story in Amtrak, the Acela Express that rides the Northeast corridor. Despite it's relatively quality relative to it's counterparts in Europe and Japan, Acela does quite well in the U.S. especially given that it trumps air travel when transit time to the airport and security is taken into account.
The blog post goes on to say what would make Acela better would be the including of wi-fi internet access on the trains to make it more appealing to business people so they would be able to work (or play World of Warcraft) while they are in transit.
It highlights one of the deficiencies of single passenger automobile travel in the U.S. that aside from listening to the news, or audiobooks. there are not a lot of ways to use your transit time. The act of driving responsibly requires you not to do too much. Mass transit and self transit provide other benefits besides transport.
When I was studying Chinese in Taipei, I found the time on the bus that it took me to get to campus was well used studying. When I walk or bike to places, I get some amount of exercise. Cars are a single tasking mode of transport, other alternatives are better on this count.