Why 48 × 40 and not something tidier
Trailer geometry decides pallet geometry. A 53-foot dry van has roughly 630 inches of usable floor length and 98 inches of width. Place GMA pallets 40-inch side across and you fit two abreast with an inch to spare; run them 15 deep and you have 30 positions.
Switch to a metric Euro pallet and you lose floor area on every trailer. That single fact keeps the GMA footprint dominant in North America regardless of fashion.
