I'm not sure about Thrifty, but all of National's cars at IAH come with a toll pass already fixed to the car. It relieves you of the need to worry about going on toll roads, but you do pay a surcharge for every day that you use it.
As noted above, a large part of the Northeastern sector of Beltway 8 is EZTag only, as is the new Grand Parkway (TX 99).
Last edited by Baritone73; Feb 6, 2016 at 8:10 am
Reason: Corrected airport code.