Texas has a project of a high speed train between Houston and Dallas, it would link the 2 cities in 90mn (instead of 3:30h of driving, or 70mn of plane. So if you spend more 20mn more at the airport than at the rail station , the train would be faster.
http://texascentral.com/the-facts/
http://www.houstonchronicle.com/local/gray-matters/article/T...
It's a privately own project, supposedly ready in 2021.