Hani Mahmassani’s Research Featured in Washington Post Story

Traffic expert Hani Mahmassani was quoted Monday in a Washington Post story about traffic.

In the article, which poses the question, “Why can’t we get anywhere?” Mahmassani, William A. Patterson Distinguished Chair in Transportation, refers to his research on traffic -- his models show how traffic becomes “unstable,” or stop-and-go.

“We see in our models that traffic becomes unstable when the number of cars [passing a specific spot] per lane per hour reaches between 2,000 and 2,500. At that nominal capacity level, traffic is very likely to become unstable,” Mahmassani says in the article.

One solution is ramp metering, where a traffic light controls the number of cars entering the highway.

“Two thousand cars per lane per hour is great, but it can’t be maintained. And when the breakdown occurs, flow rate immediately drops to around 1,200,” says Mahmassani. “The ramp meters are intended to keep the rate around 1,750 or 1,800, which is more stable.”

Read the entire article here.