• Title 49 Part 571.121 -- Air Brake Systems
• Title 49 Part 393.40 -- Required Systems
• Title 49 Part 393.43 -- Breakaway & Emergency
• Title 49 Part 393.45-46 -- Brake Tubing
• Title 49 Part 393.50 -- Reservoirs
• Title 49 Part 393.55 -- Anti-Lock Brakes

• Title 49 Part 571 Section 106

• Title 49 Part 571.108 -- Lamps, Reflective Devices, And Associated Equipment
• Title 49 Part 393.11 -- Lights & Reflectors
• Title 49 Part 393.19 -- Turn Signals

Title 49, § 393.19
Turn Signals

Sec. 393.19 Requirements for turn signaling systems. (a) Every bus, truck, or truck tractor shall be equipped with a signaling system that in addition to signaling turning movements shall have a switch or combination of switches that will cause the two front turn signals and the two rear turn signals to flash simultaneously as a vehicular traffic hazard warning as required by Sec. 392.22 with the ignition on or off. (b) Every semitrailer and full trailer shall be equipped so as to have the two rear turn signals to flash simultaneously with the two front turn signals of the towing vehicle as a vehicular traffic hazard warning as required by Sec. 392.22(a).