You’ve seen it before: a cluster of cars muscling their way from the on-ramp to the highway, causing on-coming vehicles to slow down and change lanes.

Now, thanks to a Kansas University doctoral candidate, the phenomenon has a name: platoon merge.

Hanwen Yi, a civil engineering student from Wuhan, in the Hubei province of China, coined the term after analyzing more than 120 hours of videotape of traffic on Interstate 35 in the Kansas City area. Yi developed a video image processing and data analysis software system to help civil engineers monitor traffic. Using the system, he videotaped traffic at several on-ramps along I-35 between 6:30 a.m. and 6:30 p.m. during the summer of 2003. After putting the video through his software, he categorized three types of vehicle mergers: the free merger, the challenged merger and the platoon merger.

Free mergers are those vehicles who move from the on-ramp to the highway without influencing oncoming traffic. Challenged mergers have to make speed adjustments to avoid vehicles on the highway, and in doing so may disrupt oncoming traffic. And platoon mergers move onto the highway in a cluster, causing oncoming cars to make several maneuvers which could impede traffic.

“When I gave the report to my professor, he told me I was the first one to have given these things names,” Yi said. “So I was very excited.”

While the names may be new, the concept of congested on-ramps is not. Kansas Department of Transportation metro engineer Mick Halter said anytime a vehicle merged from a ramp to the freeway or interstate, drivers must compensate with their speed in some manner. The changes in speed present a potential problem.

“Anything that would let a car or a continuous grouping of cars onto a highway all at one time has a tendency to cause a problem,” he said. “It disrupts the flow of traffic and you find that the cars will try to adjust their speed. Either you will see them speed up or slow down.”

Yi said he hoped his research findings would lead to changes in the design of on-ramps. He has developed formulas that will help engineers and designers take into account traffic patterns, such as vehicle speed, high traffic volume and on-ramp arrival patterns, when developing roadways.

Halter said KDOT was working with the Missouri Department of Transportation on researching the possibility of a new trend called ramp metering.

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Ramp metering basically would mean putting a traffic signal at the entrance point off of a ramp and onto the highway. The signal would let a few cars through every few seconds, Halter said.

“It has been shown to work quite well, but it’s not without its difficulties,” Halter said. “It’s been in use in a lot of places like Minneapolis, Los Angeles. It’s somewhat controversial, but it certainly works if it’s designed properly.”