Curing Congestion

Over half the world’s population and 80 percent of Americans live in urban areas, where land for new transport infrastructure is relatively scarce. Most roads have no tolls, and most vehicles carry a single occupant. Not surprisingly, road congestion has become a daily experience for many. 

Globally, people average about 60 minutes of travel each day, much of that consumed by stops or slowdowns. Some delays are regular and recurring, others unexpected. They are all more than just a personal inconvenience: human capital is underutilized, freight distribution delayed, meetings missed, fuel wasted, and nerves frayed.

Many important roadways regularly operate near their breaking points, and as populations and economies continue to expand, travel demands will rise and waits lengthen. Stressed transportation systems become less resilient and create cascades of real costs. As freight is slowed, food prices rise, for example; and as travel times exceed acceptable thresholds, certain destinations lose their attraction.

Thanks to new technologies we are now able to observe these systems and congestion’s effects in real time, across the large, complex scales at which they operate. We are also able to intervene at the same scale, not just locally, an approach that raises the prospect of making congestion a thing of the past.

Transportation system managers can now turn to a combination of sensors, algorithms, and system simulators to predict traffic demands from minute to minute, day to day, and year to year. In a highly instrumented system like New York City’s, signal times, tolls, and left-turn permissions can be fine-tuned in real time.

Truly reducing, rather than just managing, congestion requires active intervention to change travelers’ behavior and make the most of scarce roadway real estate. Varying tolls throughout the day in response to traffic patterns, offering slot reservations for space in some lanes, and compensating those who turn to alternatives to their own vehicle are one set of options. GPS-enabled smartphones and other technologies make such strategies much more realistic, since drivers can receive and act on information rapidly. The arrival of autonomous, self-driving vehicles that can safely travel close together should make it even easier to enhance traffic flow (see “Self-Driving Cars”).

With road space limited, over the long term travelers will need to shift to smaller vehicles, public transit, and nonmotorized modes of transport. But by acknowledging the true costs and complexity of road congestion, we can moderate it quite effectively now.

Kara Kockelman is a professor of transportation engineering at the University of Texas, Austin.