Light-rail and Traffic Congestion

An interesting article in The Washington Post’s Wonkblog caught my eye a couple weeks back addressing the issue of whether light-rail transit systems really do anything to help cut down on traffic. The argument goes that if you live in a city like Seattle that gets snarled in traffic congestion, that traffic will be reduced if you just build a train system. Those people that typically drive will choose to ride the train instead. In fact, back in September, 2008, an article published in the Seattle PI reported that a Sound Transit study found that the light rail plan “may cut traffic 30%.” While this theory seems to make sense on the surface, researchers are instead having trouble finding evidence that this is really true.

2003107323A recent study published in the Journal of Transport Geography, Do light rail services discourage car ownership and use? Evidence from Census data for four English cities, found that light-rail systems built around England during the 1990s and 2000s has had almost no effect on overall car traffic. The findings go further in suggesting that these systems are primarily attracting riders that would otherwise have taken the bus. Numerous other studies have come up with similar results – either inconclusive or very little impact.

So the question remains: what do you do to cut traffic congestion? One way the City of Seattle tried was through a program called One Less Car through Way To Go, Seattle! Now on hiatus until the spring of 2013, drivers that drove less for one month could earn up to $100 in flexcar credits, or $600 in flexcar credits could be earned by selling a car. Another article published in The Washington Post in December, 2011, points out that a few cities like Stockholm, London, and Singapore have taken different approach – taxing congestion the way one may tax pollution. Through this ‘congestion pricing’, drivers are charged for road access in busy areas and during peak hours. So far, this market-based method has proven to be the only consistent method for cutting congestion – driving people to other forms of transportation. However, there are some that argue this congestion pricing unfairly impacts lower-income people that are commuting in from areas further outside the city.

Light-rail systems, on the other hand, can lessen road traffic if they’re incorporated with a general shift toward more density. The City of Seattle is certainly on this path. As our various modes of mass transit continue to evolve and expand service, it will be interesting to monitor the impact on overall traffic congestion and single occupancy vehicles in and around the city over the next 5-10 years.


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