Straight answers to the questions you’ll have, and hear, most often when fighting a highway expansion or working to reconnect a community. These complement the Communities Over Highways Organizing Playbook.
Does adding lanes to highways solve traffic congestion?
No. Adding lanes does not solve traffic congestion in the long term. Research shows that when roads are widened, people make more trips, make longer trips, and choose to drive more often, and the cycle of traffic continues. For a brief time congestion eases, but as more people perceive that driving on the road will be easier, it attracts more drivers, and the road becomes just as congested again. This phenomenon is known as induced demand.
Houston’s Katy Freeway is an enduring example. Shortly after it was widened to 23 lanes, morning commute times on the Katy Freeway increased by 25 minutes and afternoon commute times increased by 23 minutes.
If additional lanes aren’t added (or are removed in a reconnecting communities project), where will the traffic go?
Alarmists often predict “carmageddon” if an expansion doesn’t happen, or if a highway is turned into a boulevard or city street. It doesn’t happen, because traffic doesn’t behave like water, and highways aren’t overflowing rivers. Travelers change their patterns and behavior based on the situations they face.
Just as adding lanes induces more travel, studies show that reducing capacity causes traffic to dissipate as people naturally adjust their routines. Drivers may carpool, take alternate routes, shift to public transit, or simply avoid peak hours.
How does traffic modeling work to justify highway projects?
At its most basic, traffic modeling is designed to keep cars moving at the speed limit, a measure called level of service. Level of service doesn’t measure things like access to destinations, only whether traffic flows freely. That means modeling is primed to present wider roads as the only “correct” solution, and much of it doesn’t account for induced demand.
Historically, traffic modeling has been notoriously inaccurate, consistently overestimating future traffic volumes. Most models rely on straight-line projections of past traffic counts, leaving them prone to overestimation and blind to behavioral complexity.
Want to go deeper?
The full playbook covers how highway plans get made, when and how to intervene in the process, and 17 tactics freeway fighters have used across the country.
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