I realize this is just a road, but if you have ever driven on I35 from Dallas to San Antonio, then you know that getting through Austin can be a major traffic jam. I suggest taking the SH 130 Toll Road. I’ve got a tolltag. There are no toolbooths and it’s all electronic. If you don’t have a tolltag they send you a bill in the mail.
The new extension runs from the interchange of SH 45 Southeast / SH 130 near Lockhart, Texas to the interchange of SH 130 / I-10 in Seguin, Texas. For the details on costs, I would check out the TxTag site. You can also find them on Facebook.
Disclaimer: Yeah I paid my tolls. 😉