HB 535 amends Subchapter B, Chapter 545 of the Texas Transportation Code to mandate specific safe passing distances for motor vehicles overtaking pedestrians or bicycles within municipalities with populations of 100,000 or more. It requires a minimum distance of three feet for passenger cars and light trucks, and six feet for commercial vehicles. Additional requirements include lane changes when available and clarification for passing in no-passing zones under certain conditions. The bill also introduces an affirmative defense for drivers if the pedestrian or bicyclist was violating traffic laws.