The A3002 starts on the A315 Brentford High Street and heads north. It soon crosses the A4 and then goes under the M4 - this is only a short distance west from where the motorway runs on top of the A-road. It passes to the east of Boston Manor Park before going under the Piccadilly Line by Boston Manor station.
Continuing north, Elthorne Park is now passed and then it reaches the Hanwell one-way system. Northbound traffic remains on the A3002 whereas southbound traffic uses the A4001 (marked on some maps as the A3002). Both roads end on the A4020 (former A40) in Hanwell.