M26 motorway the M26 at that time formed part of Ringway 4 and would have been designated as part of the M25. Construction of the first part of the M25 began in 1972 but before it opened, plans for the "London Orbital" motorway were modified to combine the southern and western part of Ringway 4 with the northern and eastern part of Ringway 3. To connect the two separate routes, which together were numbered as the M25, an additional section of road needed to be planned and the M25 route was diverted northwards from junction 5 to meet Ringway 3 at Swanley
London Underground The London Underground is frequently studied by academics because it is one of the largest, oldest, and most widely used systems of public transit in the world. Therefore, the transportation and complex network literatures include extensive information about the Tube system. For London Underground passengers, research suggests that transfers are highly costly in terms of walk and wait times. Because these costs are unevenly distributed across stations and platforms, path choice analyses may be helpful in guiding upgrades and choice of new stations. Routes on the Underground can also be optimized using a global network optimization approach, akin to routing