Does a combination (308, 309, 408 or 409) always need to consist of the same registered vehicles or just the same type or number of axles?

A combination does not need to consist of exactly the same registered vehicles at all times but is required to have the same number of axles.


For example, a 308 combination vehicle could have a powered vehicle with 3 axles, a 3 axle trailer and a 2 axle trailer, or a powered vehicle with 3 axles with one 5 axle trailer.