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It looked like a science-fair experiment. But it was a demonstration for legislators about a potential radical change coming to Interstate 15 in Salt Lake County.
Two Utah Department of Transportation officials poured pasta beads into clear funnels. One dumped all his beads at the same time; they quickly bottlenecked and flowed slowly out of the bottom like in an hourglass.
The other official poured his beads at a steady rate. They passed through the funnel more quickly. He was able to pour all his beads through his funnel twice before the jammed funnel emptied once.
UDOT Executive Director Carlos Braceras said that's the idea behind a concept his agency is studying, called "managed motorways," to put meters on all entrances to I-15 and tie them together into one system to allow a steadier flow.
That includes newly metering and controlling the rate of oncoming traffic from sister freeways that merge into I-15 such as Interstate 80, Interstate 215 and State Road 201.
"When a roadway is functioning well, it's moving a lot more vehicles. But when we get to a failure point, we move a lot fewer vehicles through," Braceras told the Legislature's Transportation Interim Committee this week.
"The whole idea is to optimize the flow of how traffic gets onto I-15. We can move more vehicles, more people, more efficiently if we can manage how fast the vehicles are getting on," he said. "So we're looking at a concept used in Australia."
He further explained, "We're looking at tying together all the ramp meters that we have. Right now, they operate independently."
If they operate as one system, the timing could change depending on congestion in different areas and how much room exists for more cars at various spots.
"We can see a 35 percent reduction in delay, and that includes the people sitting at ramp meters that aren't moving" at the moment, he said. "We're in a preliminary study. The results are looking very promising. We think we can get the benefits of an extra traffic lane through I-15 with this approach."
Not only that, Braceras said, but "very preliminary" projections estimate that it may cost only $35 million, a tiny fraction compared to building a new freeway lane through Salt Lake County.
The cost would include adding far more traffic and speed sensors along I-15, and expanding pavement in ramp meter areas.
The project might take two years or so to complete and could begin as soon as 2018 if evaluations prove successful, Braceras said. Many details about how it could operate are still being resolved.
Shane Marshall, deputy UDOT director, said that not as much extra ramp space may be needed as some might expect.
"Because I-15 doesn't fail, you put 35 percent more traffic through it so the ramp traffic is quicker," he said. "You just can't allow I-15 to fail, and that's where we are today" sometimes at peak drive times.
No other states have adopted such a system yet, although Braceras said a few others also are examining it.
"It's really a concept that was developed in Australia," he said, "and we have some of those folks who are managing the system in Australia working with our consulting partners right now in helping us evaluate the potential here."
Braceras added that I-15 through Salt Lake County "is the area of the state that has the most congestion," so UDOT is seeking a variety of ways to address it including managed motorways.
View a demonstration
A YouTube video showing Washington State transportation officials demonstrating with rice how metering can speed traffic is available online at goo.gl/8yimNL.