TxDOT 101: Traffic

TxDOT engineer explains how traffic works and what we’re doing to address it

By Julien Devereux

When you feel frustrated sitting in rush hour traffic, instead of thinking about how much time it’s going to take to get home, maybe you can picture a peaceful, babbling brook.

What does water have to do with traffic? TxDOT engineers who study traffic use models similar to those used in fluid dynamics—the branch of physics that studies how liquids and gases flow through their environments. In a state roadway system the goal is to let the traffic flow freely—and safely.

Of course getting stuck in gridlock is not as relaxing as tubing in San Marcos. In many ways, though, traffic behaves a little like a river.

The basic cause of a traffic jam is easy to understand: When there are enough vehicles on the road that vehicles can’t interact safely, traffic slows down. And of course, the congestion can be much worse if there is a crash, road work in progress, debris on the road, inclement weather, or any other variation from normal conditions.

This is similar to the water in a creek or river. If a river is relatively dry when heavy rains come, the water will begin to flow freely and rapidly. But if the river is already full and the rains are torrential, water begins to back up in the riverbed, slowing down while the level rises.

TxDOT engineers study traffic patterns and design roadways to maximize the flow of traffic—to keep the river flowing freely—which, in a state growing as fast as Texas, can be challenging.

“Our primary goal is safety—keeping people on our roads safe,” said Khalid Jamil, highway safety and operations supervisor in TxDOT’s Design Division. “But we are also looking at statewide solutions to congestion by looking at bottlenecks and seeing what can be done to improve them, both from a safety and congestion perspective.”

TxDOT uses real-time data from a variety of sources to monitor traffic flow around the clock. Real-time traffic conditions can be found at drivetexas.org.

TxDOT is addressing congestion in a number of ways throughout the state. The Texas Clear Lanes initiative provides funding for projects to address major chokepoints. Engineers are also creating new and innovative intersection designs, much like locks or canals to improve the river flow. A few effective new designs are roundabouts, diverging diamonds and displaced left-turn intersections.

“If the data shows that congestion is a recurring problem, this needs to be studied,” Jamil said. “We identify the chokepoint, but also examine whether bottlenecks upstream from the chokepoint might contribute to the problem. Then we look for the best solution.”

For example, if there is a slowdown along an on-ramp going uphill, engineers may decide to reduce the ramp’s angle to minimize the congestion.

However, one of TxDOT’s most important partners in its efforts to address congestion is drivers.

Following the rules of the road not only helps keep you safe, it also helps prevent crashes, fender-benders and other incidents that can create obstacles that slow down traffic. Driving safely and courteously and giving other cars adequate room to maneuver is not only good manners and safety-minded, it also helps keep the river of traffic flowing freely.

“Safety is our number one priority,” Jamil said. “Safety is incorporated into every project we make to serve the people of Texas. Traffic safety is complex, and depends on safe vehicles driven by safe drivers on safe roadways. But because most crashes happen due to driver behavior, that’s something we can all help change.”