Building bigger roads won’t make driving nicer. It will make traffic worse. That may seem counterintuitive. It’s also one of the most studied assertions of the last few decades in transport planning. A report from the University of Berkeley shows that for every 1% of extra highway capacity added, traffic volumes increase 0.9% in the longer term. When Houston, Texas expanded the Katy Freeway to 26 lanes at a cost of $2.9 billion, commute times went up. But you don’t have to look to the southern tip of a failed state for examples. Traffic volumes around the $1.4 billion Waterview Tunnel are roughly back to where they were before its construction.
This makes sense when you think about it for more than two seconds. When Apple releases new iPhones, people buy phones. When Hayden Donnell releases episodes of Get It To Te Papa, people watch Get It To Te Papa*. When governments build flash new roads, people drive. Even if the resulting traffic doesn’t clog up the motorways in question, it tends to funnel into suburban streets or smaller highways. The best we can hope for is to shift the bottleneck.
Hey, you’re onto something there. Maybe if we better used the capacity of our existing roads we wouldn’t need to spend a whole bunch of money on new ones. Perhaps we could induce some demand for public transport, cycling and walking that take up far less space, and that could reduce congestion by having fewer cars. That would free up space for the vehicles remaining.