Highway 13 (1948)

Hank Wilson is a driver for a truck for a big transportation company which is in financial straits. He is in love with Doris Lacy, a waitress at the truck-stop where the company has its truck fleet serviced. Frequent accidents near the place leads the company to hire a private detective to investigate, and when the detective is murdered Hank is arrested as a suspect. The insurance company that covers the fleet has him released and he is sent back to work with instructions to investigate the accidents on his own. The trail leads to the uncle of Doris, and one of the part-owners of the company.