A junction treatment that involves vertical separation of two or more different routes, placing them at different heights. For bicycle traffic, this will typically involve an underpass, or a bridge over a road.
While safe (there is no interaction between the two routes) and convenient (there is no delay, which might be the case with the crossing of a major road at surface level) grade separation should be carefully designed to maintain social safety, and to maximise directness.
It should also only be employed as a means of crossing through-roads, or major distributor roads.