This morning Wired worries that transportation planners will take the wrong lesson from the traffic data the Texas Department of Transportation released last week that shows that traffic is “sailing” along a three-mile stretch of State Highway 161 ever since drivers were permitted to start using the shoulders of the road. It should not be used as evidence that widening highways is a tried-and-true method of relieving congestion:
Two things might explain why the Dallas project worked. The first is that the bottleneck on that highway was a very specific problem: a two-lane stretch connecting three-lane highways. Opening the shoulders eliminated the choke points of squeezing into a tighter space.
The second and more cynical explanation for the project’s success is that it wasn’t actually successful. The traffic numbers published this month include just a few days after the new lanes opened in September. Traffic has increased since then, though the TxDOT says traffic is still moving faster than before the project. It’s quite possible unbearable congestion will return, as more locals change their behavior to take advantage of what is suddenly a smooth ride—that’s the fundamental principle of induced demand.
TxDOT told the DMN they’re already looking for other roads where this same approach might work:
“Due to the success, it’s something we’re going to look at in the future for sure,” said TxDOT spokesman Tony Hartzel.
At the top of their list is Central Expressway north of LBJ Freeway. It could take years to get federal approval and convert carpool lanes back to shoulders that would then be opened up during rush hour. But a discussion has already begun.