The idea that a highway segment can be replaced with an urban boulevard without creating significant traffic problems strikes some people as unlikely. Time and again around the world, though, highway removals have shown traffic patterns to be flexible and adaptive, with doomsday predictions of gridlock proving false. This “self-healing” nature of road networks suggests that City to River’s proposal to replace the downtown portion of (soon-to-be-former) Interstate 70 with an urban boulevard is likely to cause minimal adverse effects on the vast majority of drivers traveling through the St. Louis area.
Although it seems counterintuitive, many traffic experts understand that creating more road capacity via highways actually tends to increase congestion in urban areas. Highways force (or, at least, cause) too many drivers to use a single route that often has inadequate access points to a city, rather than distributing the traffic more evenly over a network of roads. High-speed routes introduce inefficiencies by inducing drivers to go out of their way in an attempt to save a minute or two, as opposed to taking a more direct route on local streets. Even the mere ability of drivers to move faster can cause traffic problems. As explained in a 2006 SmartMobility report, “[s]peed is confused with capacity. An urban street can carry more vehicle traffic at 30 m.p.h. than it can at 50 m.p.h. because the capacity is controlled at signalized intersections.”
More and more cities are recognizing the problems caused by highways cutting through their urban cores, and the benefits that can be achieved when those highways are removed. Highway removal and restoration of the urban grid thus has become a preferred choice for an ever-growing number of cities. Even the U.S. Department of Transportation has recognized that replacing an urban highway with a surface boulevard is the more financially and environmentally sensible choice for some cities, and is consistent with USDOT’s goal of ensuring that “[p]edestrians, bicyclists, motorists and public transport users of all ages and abilities are able to move safely and comfortably along and across a complete street.”
When a highway is eliminated, traffic tends to adapt quickly. Drivers spread across grid networks, with replacement streets serving much of the same traffic and previously underutilized routes absorbing the rest. Often, traffic in the impacted area appears to simply “disappear,” as drivers adopt alternative routes, travel times, and even modes of transportation. As noted in a 1998 study that analyzed the effects of seventy cases of reduced road capacity (although not necessarily highway removal), “traffic problems are usually far less serious that predicted,” and “widespread, long-term disruption is hardly ever reported.”
These are more than abstract theories, but rather have been proven time and again in successful urban highway removals around the world. Here are just a few examples of highway removals that have not caused the major traffic problems predicted by experts and feared by the public: