Seat belts of a transport system are provided with anti-submarining seat-belt assemblies. A lap-belt portion of each assembly, restraining the lower part of the body of a belted passenger, is subdivided into two anti-submarining belt portions, which properly restrain the thighs when plug-in connecting at least one anti-submarining latch-plate to one of the anti-submarining buckle assemblies, all of which, equipped with energy absorbers, are arranged in a seat cushion. As a result, the energy-absorbing, anti-submarining seat-belt assembly substantially lowers great belt force in an accident, reduces the elongation of the seat belt and prevents submarining.A separately operated release button, when depressed, frees the passenger from the anti-submarining protection.Ease of use is ensured by one-click operation of a master release-button, which, when depressed, releases all latch-plates.Detachable anti-submarining latch plates, when not in use, are stored in a storage box. When needed they are attached to the lap-belt portion.