Motorists face a 'perfect storm' of Olympic gridlock as the first three days of the sporting extravaganza face being crippled by jams chaos, an alarming report by leading traffic experts warns.
The report says the Olympic opening ceremony on Friday 27th July clashes with one of the busiest holiday getaway weekends of the summer when traffic levels are already around 30 per cent above average.
It stresses: 'The first three days of the event pose the greatest risk of traffic troubles.'
'The combination of high expected attendance figures, extensive road closures and normal holiday getaway traffic with a road user population in the early stages of learning how to cope with changes to normal traffic flows caused by events means the event could get off to the worst possible start.'
The dire prediction is made by global traffic experts INRIX - the firm which provides vital real-time traffic information to hundreds of sat-nav and mobile phone providers, including car giants such as Ford, Audi, Nissan Toyota, as well as to the BBC.
It is based on its detailed data of current historic traffic flows gathered over many years - including disruption caused by major sporting or cultural events - combined with their prior diary knowledge of Olympic and other events planned this summer.
The INRIX report notes how Transport Secretary Justine Greening and Olympic planners are relying on city workers switching to public transport, staggering their journeys, or working from home, to ease the congestion.
But it warns: 'If there is at any stage a failure of the transport system to cope with the demands put on during this period there is a danger that this could be the lasting memory… rather than the sporting excellence achieved by the athletes.'
It notes: 'The danger of a 'domino effect' of congestion routes near to the M25 blocking key junctions and preventing access to and from the motorway is clearly a significant risk. The worst case outcome could be that congestion builds around the whole motorway as occurred with the Robbie Williams concert at Knebworth in 2003.'
The men's and women's road cycling events are also being held over that first Olympic weekend: 'These will require thousands of road closures to be implemented throughout South West London and around the county of Surrey.'
Preparatory dry-runs in August 2011 saw traffic 'descend into chaos', it noted: 'Journeys of just a few miles took several hours and some drivers were forced to abandon their cars.'
It concludes: 'The organisers are therefore at significant risk of having the first three days dominated by stories of serious traffic problems – a 'Perfect Storm' of traffic congestion.'
It adds: 'The sight of the Opening Ceremony commencing in front of a half-empty stadium due to spectators being held up in serious traffic congestion would be the worst possible start to proceedings.'
By contrast, elite Olympic VIPs will be spared the jams because they have exclusive use of more than 250 miles of the nation's busiest roads. Up to 80,000 officials, sponsors, politicians and athletes - dubbed 'the Games Family' - will be whisked seamlessly down specially reserved congestion-free lanes in a fleet of up to 4,000 low and zero polluting BMW and MINI vehicles – including electric and hybrid powered cars.