M25 motorway Europe's second longest orbital road after the Berliner Ring, which is . Originally built almost wholly as a dual three-lane motorway, much of the motorway has been widened: to dual four lanes for almost half, to a dual five-lanes section between junctions 12 and 14 and a dual six-lane section between junctions 14 and 15. Further widening is in progress of minor sections with plans for managed motorways in many others. To the east of London the two ends of the M25 are joined to complete a loop by the non-motorway A282 Dartford Crossing of the River Thames between Thurrock
M25 motorway "rings" around the capital. Sections of the two outer rings – Ringway 3 (the 'M16 motorway') and Ringway 4 – were constructed in the early 1970s and were integrated into the single M25 orbital motorway. But the Ringways plan was hugely controversial owing to the destruction required for the inner two ring roads, (Ringway 1 and Ringway 2). Parts of Ringway 1 were constructed (including West Cross Route), against stiff opposition, before the overall plan was abandoned in 1973 following pressure from residents in the threatened areas. Construction of parts of the two outer ring roads, Ringways 3 and 4,