49 CFR 383.115 - Requirements for double/triple trailers endorsement.
(a) Procedures for assembly and hookup of the units;
(b) Proper placement of heaviest trailer;
(c) Handling and stability characteristics including off-tracking, response to steering, sensory feedback, braking, oscillatory sway, rollover in steady turns, and yaw stability in steady turns;
(d) Potential problems in traffic operations, including problems the motor vehicle creates for other motorists due to slower speeds on steep grades, longer passing times, possibility for blocking entry of other motor vehicles on freeways, splash and spray impacts, aerodynamic buffeting, view blockages, and lateral placement; and
(e) Operating practices and procedures not otherwise specified.