Denham Roundabout, alt=Denham Roundabout, with a blue one-way road sign The Denham Roundabout is a road junction in Denham, Buckinghamshire. It was originally opened in 1943 in conjunction with the completion of the new Western Avenue route into west London. The Western Avenue took over the classification of the A40, with the previous route to London, via Uxbridge and Ealing, being reclassified as the A4020. The roundabout also included a new link to A412 that formed part of the outer London orbital route. Since 1973, the westbound A40, now flows into the

M40 motorway The M40 motorway links London, Oxford, and Birmingham in England, a distance of approximately . The motorway is dual three lanes except for junction 1A to junction 3 (which is dual four lanes) a short section in-between the exit and entry hig ...

at this point. The

roundabout A roundabout, a rotary and a traffic circle are types of circular intersection or junction in which road traffic is permitted to flow in one direction around a central island, and priority is typically given to traffic already in the junct ...

below facilitates junction 1 (J1) of the motorway to connect with the westbound continuation of the A40, together with the intersection of the road from

Uxbridge Uxbridge () is a suburban town in west London, England, and the administrative headquarters of the London Borough of Hillingdon, northwest of Charing Cross. Uxbridge formed part of the parish of Hillingdon in the county of Middlesex. As part ...

( A4020) and the road from

Slough Slough () is a town in Berkshire, England, in the Thames Valley, west of central London and north-east of Reading, at the intersection of the M4, M40 and M25 motorways. It is part of the historic county of Buckinghamshire. In 2021, the ...

Watford Watford () is a town and non-metropolitan district with Borough status in the United Kingdom, borough status in Hertfordshire, England, northwest of Central London, on the banks of the River Colne, Hertfordshire, River Colne. Initially a smal ...

( A412). When the M40 from Denham to

High Wycombe High Wycombe, often referred to as Wycombe ( ), is a market town in Buckinghamshire, England. Lying in the valley of the River Wye, Buckinghamshire, River Wye surrounded by the Chiltern Hills, it is west-northwest of Charing Cross in London, ...

was built, Western Avenue was extended at high level to make an end-on join with the motorway, and a larger roundabout was built below the bridges carrying the motorway. When first laid out, the roundabout had the traffic going round it clockwise in the usual way, but as traffic volumes built up, the layout was altered so that the traffic moved round the roundabout in both directions, making it a ring junction with roundabouts at the points that other roads join the main roundabout.

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Google Maps satellite image view
Magic roundabouts Roundabouts in England Road junctions in England Transport in Buckinghamshire {{England-road-stub

See also

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