The loading gauge is the gauge or profile up to which a vehicle can be loaded in order to maintain a minimum clearance between the loaded top of the wagon and the underside of a structure such as a bridge, tunnel, or signal post. The dimensions of the load of the wagon are kept within the fixed limits by erecting a loading gauge across the track in the shape of a steel frame, which causes an obstruction if
the wagon is loaded to an extent that exceeds the loading gauge (see Fig. 2.2 in Chapter 2).
Loaded wagons whose dimensions exceed the normal permissible loads are known as oversized dimensioned consignments (ODCs). ODC parcels can also be sanctioned up to a certain level after taking the following precautions.
(a) Trains carrying ODCs should move at a restricted speed, which is specified for the purpose.
(b) Such trains should not move at night.
(c) Train carrying ODCs should be accompanied by a supervisor whose duty is to ensure the safely of the train along the route.