MARC trains will get you from Rockville to Columbia(environs, anyway) about and hour, total--this may seem like a lot of time, but it beats what it would take you to drive during rush hours, and you can read, do work, or even make phone calls enroute--and it is not subject to traffic delays, as car and van pools are--withnew the Verizon wireless connections, it is even possible to connect to the internet while on the train--