What safety feature automatically activates on an articulated semi-trailer if it accidentally detaches from the tractor unit while driving (挂车脱钩事故)?

1. The severed pneumatic supply line dumps air pressure, causing the trailer emergency relay valve (挂车继动阀) to apply full spring emergency braking, stopping the detached trailer
2. The trailer wheels automatically steer toward the right-hand ditch at 45 degrees
3. The trailer activates auxiliary electric motors to drive itself to the nearest service area
4. The trailer parachute deploys from the rear doors to slow aerodynamic momentum