It starts at traffic lights on the A308 King's Road and heads northwest for about a quarter of a mile to reach the A304 Fulham Road where it ends at a set of traffic lights.
Originally, it continued further. It multiplexed west along the A304 Fulham Broadway before turning right into Jerdan Place to regain its number. After crossing the B317 North End Road it continued along Dawes Road most of the way to Fulham Cemetery before ending on the A3218 Lillie Road.
That part of the B318 north of the A304 was quickly upgraded to Class I status, becoming the A3219. However, Jerdan Place is now largely pedestrianised.