In October we described the “fundamental law of road congestion,” which explains that building more roads fails to decrease congestion, and in fact increases it, because doing so tempts more people into their cars. The authors of that paper believe the most effective response to city traffic — nay, the only one — is congestion pricing.

Of course that doesn’t mean it’s a perfect solution. In response to our October post, Felix Salmon at Reuters argued that congestion pricing is a perpetually unpopular approach to clearing city traffic. At first, drivers are upset they must pay more to use the same route they’ve always used. As congestion pricing clears roads, it inevitably induces some additional demand, and traffic increases, so that prices must be raised even more. And so the fight continues.

Still that fight seems worthwhile — provided that pricing truly eases congestion. At least one transportation scholar isn’t so sure. In an upcoming issue of Urban Studies, Moshe Givoni of the University of Oxford offers a detailed examination of London’s congestion pricing system and concludes that “questions can be raised with regard to its practical effectiveness.”

London began its pricing program in 2003. At first the benefits were enormous: in response to the rising cost of driving into the city, congestion fell by roughly 30 percent. But those gains quickly reached a plateau, and since then congestion has started to near its pre-pricing levels, Givoni reports:

In London, congestion is measured as the average excess delay (minute/km), which is the delay to traffic compared with the free-flow speed — the average speed during night time. In 2002, the average excess delay on roads inside the CC [congestion charging] zone was 2.3 min/km — the base congestion level before CC was introduced. This had fallen to 1.6 min/km in 2003, the often-quoted 30 per cent reduction in congestion. The level of congestion remained the same in the following year but started to increase thereafter. In 2005 and 2006 it increased to 1.8 and 2.1 min/km respectively. Thus, congestion has almost returned to its pre-charging level in 2006.

Read the entire article at: Atlantic Cities

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