"A Globe analysis of state highway data documents what many motorists have come to realize since the new Central Artery tunnels were completed: While the Big Dig achieved its goal of freeing up highway traffic downtown, the bottlenecks were only pushed outward, as more drivers jockey for the limited space on the major commuting routes."
"Ultimately, many motorists going to and from the suburbs at peak rush hours are spending more time stuck in traffic, not less. The phenomenon is a result of a surge in drivers crowding onto highways - an ironic byproduct of the Big Dig's success in clearing away downtown traffic jams."
"The upshot is that Massachusetts, for the $15 billion invested by the state and federal taxpayers, got a gleaming new highway system that has made zipping beneath Boston and Boston Harbor much easier. It increased overall mobility by allowing more people to travel at peak times. But most travelers who use the tunnels are still spending time in traffic jams - just not in the heart of the city, where bumper-to-bumper was a way of life on the old elevated artery."