In which order should trailers be placed when making up a doubles combination?

TRAILER ORDER in doubles and triples combinations is a safety consideration, not just a logistics preference. THE RULE: Heavier trailer immediately behind the tractor; lighter trailer on the converter dolly. REASON — STABILITY: A heavy rear trailer increases rearward amplification because it has more inertia to swing outward in turns and lane changes; a heavy rear trailer also generates greater jackknife-inducing forces if its brakes become imbalanced; placing the heavier load closer to the tractor's direct control (the fifth wheel) reduces the amplified swing forces on the last unit; WEIGHT DISTRIBUTION: The heavier load also distributes more weight through the tractor's drive axles when placed directly on the fifth wheel, which improves traction; FEDERAL REGULATIONS: 49 CFR Part 393 addresses vehicle combination stability; while specific weight order regulations vary by state, the general principle of heaviest first is consistent with engineering guidance for LCV (Long Combination Vehicle) operation; PRACTICAL NOTE: When picking up trailers, if you do not know their weights, check the bills of lading for cargo descriptions and estimate which is heavier; when in doubt, check with the carrier — they should provide guidance on trailer order for mixed-weight loads.