Editing M25 motorway (section)

===Features===

The M25 was originally built mostly as a dual three-lane motorway.{{sfn|Hamilton|2015|p=25}} Much of this has since 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 [[smart motorway]]s in many others.<ref name=bp/>

Two [[motorway service area]]s are on the M25, and two others are directly accessible from it. Those on the M25 are [[Clacket Lane services|Clacket Lane]] between junctions 5 and 6 (in the south-east) and [[Cobham services|Cobham]] between junctions 9 and 10 (in the south-west). Those directly accessible from it are [[South Mimms services|South Mimms]] off junction 23 (to the north of London) and [[Thurrock services|Thurrock]] off junction 31 (to the east of London).<ref name = cobhamServices>{{Cite web |publisher=[[Highways Agency]] |title=M25 MSA New Barn Farm Cobham |access-date=14 August 2010 |url=http://www.highways.gov.uk/roads/projects/26511.aspx|archive-url=http://webarchive.nationalarchives.gov.uk/20100303165935/http://www.highways.gov.uk/roads/projects/26511.aspx |archive-date=3 March 2010}}</ref><ref name=CobhamOpen>{{cite news |url=https://www.bbc.co.uk/news/uk-england-sussex-19583309 |title=Cobham M25 service station opened |date=13 September 2012 |work=[[BBC News]] |access-date=13 September 2012}}</ref>

As is common with other motorways, the M25 is equipped with emergency ("SOS") telephones. These connect to two [[National Highways]] operated control centres at [[Godstone]] (for junctions 1 to 15 inclusive) and [[South Mimms]] (for 16–31). The Dartford Crossing has a dedicated control centre. There is an extensive network of [[closed-circuit television]] (CCTV) on the motorway so incidents can be easily identified and located. A number of [[four-wheel drive|4×4]] vehicles patrol the motorway, attempting to keep traffic moving where possible, and assisting the local police. They can act as a [[rolling roadblock]] when there are obstacles on the road.{{sfn|Hamilton|2015|p=24}}

When completed, the M25 only had [[street lighting]] for {{convert|65|miles}} of its {{convert|117|miles|adj=on}} length.<ref>{{cite web|url=https://hansard.parliament.uk/commons/1986-02-06/debates/0a2b2f7d-26ea-4c54-90e7-7aa69c07f435/Roads(LightingAndSigns)|title=Roads (Lighting and Signs)|first=Nicholas|last=Ridley|author-link=Nicholas Ridley, Baron Ridley of Liddesdale|work=Hansard|date=6 February 1986|access-date=13 May 2019}}</ref> Originally, [[sodium vapor lamp|low pressure sodium]] (SOX) lighting was the most prominent technology used, but this has been gradually replaced with high-pressure sodium (SON) lighting. {{asof|2015}} the motorway has more than 10,000 streetlights.{{sfn|Hamilton|2015|p=26}} The M25 has a number of pollution control valves along its length, which can shut off drainage in the event of a chemical or fuel spill.{{sfn|Hamilton|2015|p=26}}