Autonomous driving is becoming increasingly widespread. Waymo self-driving cars are zipping passengers around more and more cities, while driverless AI trucks are hauling freight across Texas in trials. Yet one obscure law could bring any further advancement of this relatively new industry to a standstill.

Deep in the many pages of federal regulations governing the trucking industry lies Section 392.22 of Title 49, which outlines precisely what needs to happen when a commercial motor vehicle breaks down on the road. First, the vehicle's hazard warning signal flashers must be activated. The hazard lights must remain flashing until either three approved bidirectional emergency reflective triangles or at least six fusees/three liquid-burning flares are physically placed in very precise locations around the truck within 10 minutes.

While enacting the hazard warning signal system can easily be accomplished by the onboard computer or a remote operator, physically setting down warning markers can't be done without the presence of humans -- especially because one must be placed exactly four paces (about 10 feet) from the stopped rig on the traffic side, in the direction of approaching traffic. Plus, a second device must be dropped 40 paces (100 feet) away from the vehicle in the same direction as approaching traffic, but this time either in the center of the traffic lane or shoulder, depending on where the truck is located. Finally, a third needs to be placed 40 paces in the same lane or shoulder, this time away from approaching traffic.