Under what circumstance is it lawful for the driver to back up on a controlled access highway?

Backing up on a controlled access highway is extremely dangerous due to the high-speed nature of traffic on these roads and the limited access points. Thus, the transportation code clearly prohibits it in all scenarios, emphasizing that drivers must adhere to the traffic regulations that prioritize safety and the smooth flow of traffic on such highways. This prohibition ensures that all drivers are held to a standard that minimizes the risk of accidents related to vehicles reversing on these types of roadways. As a result, there are no exceptions that would lawfully allow a driver to back up, making this the correct answer. Other options imply that there may be conditions under which backing up is allowed, which contradicts the strict regulations in place for maintaining safety on controlled access highways.