The M25 is only operating at 12% capacity if you take into account the empty seats in cars and numbers of vehicles driving in off peak times compared to peak times, TRL's transportation division senior consultant Simon Notley told an audience at the Traffex show last week.

"Only 44% of vehicle capacity is actually used over a 24 hour period," he said, "and there are 3.6 empty people spaces per car on average."

If you assume an average of five seats per car and you fill all the cars you get from a person flow of 168 people/minute to 600 people a minute, Mr Notley said. Likewise if the motorway operated at full capacity for 24 hours the amount of traffic it could carry would be doubled.

"There are significant things (to maximise capacity of motorways) that don't involve technology but changes to culture," he said in a presentation about the future of managed motorways. This would include a mass move to car sharing with strangers, he added.

Mr Notley also painted a picture of a time when in car technology would cancel out the need for investment in on-road intelligent transport technology. Sat Nav, GPS data, adaptive cruise control and vehicle to vehicle communications will change how people drive and what routes they take, he said. 

"And if we have ubiquitous vehicle position data fed back to a central resource there would be no need for inductive loops in the roads and other infrastructure based interventions."

Intelligent cars would be capable of forming platoons at close quarters, and create their own best options for speeds and routes, Mr Notley said. But if a national managed plan for optimal traffic behaviour was needed those cars would have to be provided with instructions and strategy again from a central resource.

Given the 'spare' capacity currently in existence, "I am asking is it worth it?" he said.

Photo: Nigel Cox

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