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 truckstop 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 partowners of the company