coupler

Instead of using traditional railroad couplers or magnets to attach cars, the cars use their motors to stay connected.

A company rule bars towing waybill locomotives without such couplers, the report said.

The transit system has rebuilt much of the “coupler” system, and it began slowly phasing in the cars in October.

In most instances, crews repaired the breaches using a sleeve-like steel coupler, referred to as a “boot,” to patch over the hole.

The coupler involved in the 2018 separation had a bolt that was the wrong size, Metro Chief Safety Officer Theresa Impastato said last year.