The US government is responsible for major freeways such as I-35 and highways such as US 183, the state of Texas constructs other major highways such as TX 29 and farm-to-market roads such as RM 1431, and cities such as Cedar Park and Round Rock build and maintain roads within their city limits. The county government builds and maintains a network of roads in all other areas of the county.

Williamson County has a network of around 1,469 miles of County roads which is growing rapidly as the population grows. The County may purchase right-of-way and construct new roads, but more often the County accepts roads deeded by developers if they meet County standards. The County also builds bridges and grade-level crossings and installs culverts. The County maintains road beds, shoulders, road markers, water crossings, and land in the right-of-way. For more information, please see the answers to Frequently Asked Questions.