Longest Lane

In the early days of SABRE the question was asked about The Longest Lane. In other words, if a driver entered a certain road lane at a junction, what was the furthest distance he could travel without changing lanes? A lane could pass through a signalised junction provided that the lane continued or resumed without ambiguity - but if the route through the junction was unclear, or a roundabout was reached, then the lane would end.

The result was a surprisingly long route between west London and south London.

Starting at Hyde Park Corner, the Longest Lane heads west along the A4 to reach the M4, then from there as far as J20. The lane turns off to join the northbound M5, following it to J4A where it turns off again to join the M42. The lane passes straight through J3A, becoming the M40 and following this road to its end, where it turns into the A40. The lane continues into central London, going along the Westway onto the A501 and following this to traffic lights just past King's Cross Station, where it forks right onto the A201. This is then followed southwards under the Holborn Viaduct and over Blackfriars Bridge to end at St George's Circus. En route the lane itself switches position on the road, sometimes as the left lane and (more frequently) further right.

The direct route between the two ends of the Longest Lane, past Buckingham Palace and across Westminster Bridge, is just over 2 miles.

The route has not been resurveyed in the interim period and so it is possible that the Longest Lane has been shortened, or even that the actual longest road lane is now elsewhere.

Links

The original SABRE forum thread where the question is put and the route discussed