Effective width

Effective width refers to the usable width of cycling provision.

This will be substantially narrower than the absolute width if - for instance - a cycle track is bordered by high kerbs, or by a wall, or planters. 

Effective width less than absolute width

Proper cycle infrastructure design should allow the full absolute width of a cycle track to be used, with the employment of shallow, angled kerbing that allows people to cycle right on the very edges of the cycle track. The effective width matches the absolute width.

Effective width same as absolute width

This kerbing has the additional advantage of being traversed more easily by pedestrians.