Driving along Interstate 5 in Stockton is not a pleasant experience these days: the pavement is littered with potholes, heavy equipment dominates the landscape and shoulder access is restricted by concrete barriers. But many Stocktonians don’t mind the inconvenience because the $262 million lane-widening project signals progress. Likewise, Highway 99 will be upgraded and expanded for a price tag of $250.5 million. To several, these new lanes can’t come fast enough. Local rush hour traffic feels like it has reached Los Angeles or Bay Area grade levels, but once there are more lanes, traffic will disappear!
Sounds like a great plan, too bad it won’t work. Over the long term, these “congestion relief” improvements will not reduce traffic and will most likely make congestion worse for Stocktonians and visitors alike.
How can I make such a brazen statement? Because every other region that tries to build its way out of congestion ends up with more traffic, not less, and there is plenty of data to back that up. At first, this notion may seem counterintuitive: wider freeways means more space for cars which should mean less traffic, right? Unfortunately, this axiom is fatally flawed by two words: induced demand.
The concept of induced demand is simple: when you supply more of a good, more people will consume it. There may be no better example of induced demand than traffic. As more lanes open up on a highway, more people start using those lanes, meaning more people overall are driving, eventually leading to even more congestion. This specific phenomenon is known as “induced traffic.”
Research on induced traffic repeatedly shows that more roads mean more congestion. In 1998, an expansive analysis of over 70 cities by the Surface Transportation Policy Project found that for 90 percent of new urban roadways, it takes only five years for congestion to return.
The study also found that areas spending the most on highway construction actually end up with slightly higher amounts of congestion, fuel costs and travel delays than areas that spend less.
Since 1998, there have been several studies that reinforce these findings. A 2004 study found that new lanes are filled to capacity in just a few years.* In 2009, a National Bureau of Economic Research report concluded that building additional roadway almost always leads to a corresponding increase in traffic. The report’s data “suggest[s] that an average extension of the interstate network does not result in sufﬁcient travel time improvements to justify its cost.” I could go on, but you get the point.
Even measures like carpooling can’t justify more lanes. In Stockton, the Interstate 5 lane widening may feature High-Occupancy Vehicle (HOV) lanes, though Bay Area researchers found that added HOV lanes actually increased congestion while not encouraging carpooling.
There is no reason to think that the fate of traffic in Stockton will be any different. This is not to say that there will be absolutely no good to come of these projects. Our share of Interstate 5 is in dire need of repaving as poor road conditions diminish fuel efficiency and exacerbate wear and tear. And of course any money being spent here on construction surely helps the local economy. Even at their onset, these new lanes probably will ease traffic, if only for a few years. However, with a price tag of over $500 million, are these projects worth the cost? I personally do not believe they are, especially when you remember that 1,025 trees were uprooted— without a commitment from Caltrans to replace them– to make room for these new lanes.
The state and region would be much better served investing some of this highway money on overlooked and underfunded transportation modes, such as rail and bike lanes. At the very least, priority should be given to projects that can actually make driving more efficient, such as renovating bridges and repaving. Simply put, the cost of widening highways is not worth the benefit.
*This study and the STPP study are quoted from “Walkable City” by Jeff Speck.