Beware of false ‘untangled’ benefits

IN ONE of the world’s most ambitious transport projects involving refashioning freeways, the US city of Boston rerouted its central artery, the Interstate 93, into a 5.6km tunnel, freeing the surface land for other public uses.

Planning for what became popularly known as “Big Dig” began in the early 1980s, with an anticipated completion date of 1998 and a price tag of $2.8billion (R42.3bn).

In the end the project was plagued by escalating costs and schedule overruns and turned out to be the most expensive highway project undertaken in that country.

It was finally completed in 2007 at a cost of between $14.6bn and $22bn (the latter sum reportedly including interest, which is not expected to be paid off until 2038).

For motorists, a state commission found, the benefits were undoubted. Boston traffic was “untangled”, with a 62 percent reduction in vehicle hours on the Interstate 93, from an average of 38 200 hours a day before construction to 14 800 hours a day.

The savings for travellers were estimated towards the end of the project at $166 million a year.

However, a 2008 Boston Globe study found “waiting time for the majority of trips actually increased as a result of demand induced by the increased road capacity”.

The newspaper found that because more drivers were opting to use the new roads, traffic bottlenecks were only pushed outward from the city, not reduced or eliminated, even though some trips were faster.

The Boston Globe said the earlier statecommissioned study “did not look at highways outside the Big Dig construction area, and did not take into account new congestion elsewhere”.