When traffic-clogged highways are expanded, new drivers quickly materialize to fill them. What gives? Here’s how “induced demand” works.
Benjamin Schneider is freelance writer and former editorial fellow at CityLab.
Sep 6, 2018
It’s time again for “CityLab University,” a resource for understanding some of the most important concepts related to cities and urban policy. If you like this feature, have constructive feedback, or would like to see a similar explainer on other topics, drop us a line at editors.
With 26 lanes at its widest point, the Katy Freeway in the Houston metro is the Mississippi River of car infrastructure. Its current girth, which by some measures makes it the widest freeway in North America, was the result of an expansion project that took place between 2008 and 2011 at a cost of $2.8 billion. The primary reason for this mega-project was to alleviate severe traffic congestion.
And yet, after the freeway was widened, congestion got worse. An analysis by Joe Cortright of City Observatory used data from Houston’s official traffic monitoring agency to find that travel times increased by 30 percent during the morning commute and 55 percent during the evening commute between 2011 and 2014. A local TV station found similar increases.
The Sisyphean saga of the Katy Freeway is a textbook example of a counterintuitive urban transportation phenomenon that has vexed drivers, planners, and politicians since the dawn of the automobile age: induced demand.
- In urbanism, “induced demand” refers to the idea that increasing roadway capacity encourages more people to drive, thus failing to improve congestion.
- Since the concept was introduced in the 1960s, numerous academic studies have demonstrated the existence of ID.
- But some economists argue that the effects of ID are overstated, or outweighed by the benefits of greater automobility.
- Few federal, state, and local departments of transportation are thought to adequately account for ID in their long-term planning.
Nearly all freeway expansions and new highways are sold to the public as a means of reducing traffic congestion. It’s a logical enough proposition, one that certainly makes plenty of sense to anyone who’s stuck in traffic: Small communities served by small roads grow bigger, and their highways need to grow with them. More lanes creates more capacity, meaning cars should be able to pass through faster. But that’s not what always happens once these projects are completed.
Traffic Jam? Blame ‘Induced Demand.’ – CityLab
When traffic-clogged highways are expanded, new drivers quickly materialize to fill them. What gives? Here’s how “induced demand” works. Benjamin Schneider @urbenschneider Feed Benjamin Schneider is freelance writer and former editorial fellow at CityLab. Sep 6, 2018 It’s time again for “CityLab University,” a resource for understanding some of the most important concepts related to… [Read More]