In 2008, the state of New Hampshire dished out over $600 million to expand and redesign 18 miles of the I-93 highway that stretches from Manchester to the Massachusetts border. With this addition of two lanes going either way, many expect the congestion problem that plagues the highway to disappear. There has even been talk of using one of the new lanes to accommodate only bus transit. Will the expansion of I-93 relieve traffic congestion problems?
While this logic seems sound enough, there is evidence that if this highway expansion does provide congestion relief, it will only be temporary. One of the main problems of highway expansion is the “induced demand” phenomena. Induced demand works on open highway lanes exactly the way it is stated, it draws users. Study after study has confirmed that the induced demand effect is real. In a study by Mark Hansen, adding lane-miles does induce substantial new traffic – a 100% increase in lane-miles induces a 90% increase in vehicle-miles within five years.[1]
If New Hampshire is destined for highway congestion in the future despite increasing highway capacity, policy makers will need to look at other policy levers to prevent traffic problems, including land use practices to control development and incentives for the use of alternative transportation.
Currently, the state has an opportunity to use federal stimulus dollars to develop commuter rail capacity. Highway expansion is not a panacea. Despite additional investment in transportation over the high price of the 93 project, should the state let the opportunity for comprehensive transportation development to drive by?
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