M25 motorway the east of Gravesend and Grays, the Lower Thames Crossing, in order to relieve congestion on the A282 Dartford Crossing and connect the M25 at North Ockendon in Essex with the M2 in Kent. At Junction 5, the clockwise carriageway of the M25 is routed off the main north–south dual carriageway onto the main east–west dual carriageway with the main north–south carriageway becoming the A21. In the opposite direction, to the east of the point where the M25 diverges from the main east–west carriageway, that carriageway become the M26 motorway. The radial distance from London (taken as Charing Cross) varies
M40 motorway A412 southbound. The original line of the A40 can be seen going straight through the roundabout. The motorway carries on for another before it reaches J1a, the free-flow interchange with the M25 London Orbital. It is a partially unrolled cloverleaf, with the smoothest turns from the London-bound M40 (from Oxfordshire, Warwickshire and the wider West Midlands) to the anti-clockwise M25 (London Heathrow, Gatwick, The Channel Ports) and vice versa, since this is the largest exchange of traffic between the two motorways. The M40 passes over the interchange, with the M25 on the bottom. The clockwise M25 enters the junction with