According to the 2001 Urban Mobility Study, compiled by the Texas Transport Institute with the assistance of 11 state departments, ‘rush hour’ in the US’s major cities has doubled in less than 20 years, now taking up nearly half of the daylight hours in any given work day. On average, delays total 36 hours per year per commuter, with an average ‘rush hour’ trip taking 32% longer than the same trip in non-congestion conditions.

The problem requires a number of solutions, according to the Texas Transport Institute, with road expansions only serving to slow the growth in congestion, and many of the worst congested areas lacking the space, money and public approval. Information technology and intelligent transport systems are also part of the answer, as is changing the way that travellers use the network, making walking, bicycling and public transport more attractive. With no further growth in road building, car-sharing would have to account for, on average, an increase of 0.04 people in each car per year or, in other words, four out of every 100 vehicles would have to become a new two-person carpool to handle one year’s growth. The report’s authors express doubts as to whether this number of people in the US could be persuaded to share their journeys.

“Widening roads is part of the solution, but it’s only one of many elements we need to address the problem,” said Tim Lomax, one of the authors of the report.

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