This year’s scheduled completion of a $15 billion automatic railroad braking system will bolster the industry’s argument for eliminating one of the two crew members in most locomotives.

But labor groups argue that single-person crews would make trains more accident-prone.

The shift away from two-person crews would jeopardize thousands of jobs at the major railroads and continue the decades-long trend of shrinking crews.

The industry is on the verge of widespread use of an automatic braking system railroads say makes it unnecessary to have a conductor in the cab. But labor groups say conductors provide a crucial safety backup.