M25 motorway and Thurrock off junction 31 (to the east of London). Cobham services opened on 13 September 2012. Originally, the M25 was unlit except for sections around Heathrow, major interchanges and Junctions 23–30. Originally, low pressure sodium (SOX) lighting was the most prominent technology used, but widening projects from the 1990s onwards have all used high-pressure sodium (SON) lighting and this has diminished the original installations. By 2014 only one significant stretch was still SOX-lit (Junction 25–26) and the units were removed the same year. The motorway passes through five counties. Junctions 1A–5 are in Kent, 6–14 are in Surrey, 15–16
M25 motorway opened in 1986 traffic levels exceeded the maximum design capacity and in 1990 the Secretary of State for Transport announced plans to widen the whole of the M25 to four lanes. By 1993 the motorway, which was designed for a maximum of 88,000 vehicles per day, was carrying 200,000 vehicles per day. 15% of UK motorway traffic volume was on the M25 and there were plans to add six lanes to the section from Junctions 12 to 15 as well as widening the rest of the motorway to four lanes. In parts, particularly the western third this plan went ahead,