The Drive: Study cites commuter behavior for congestion on I-35W

  • Article by: TIM HARLOW , Star Tribune
  • Updated: September 29, 2013 - 8:17 PM

Anybody who drives on Interstate 35W between the Crosstown and downtown Minneapolis knows that rush hours can make for a dashboard-pounding commute. It’s only about 5 miles, but the trip can take as long as 20 minutes.

A new study indicates that commuters may be to blame for some of that.

Over the past few years, MnDOT has added several features on 35W to help reduce travel times. They include more general-purpose lanes, a MnPass lane, Smart Lane technology and the 46th Street Transit Station. The improvements have yielded only moderate success in reducing congestion, partly because commuters are not taking full advantage of them.

That’s the conclusion of John Hourdos, a researcher at the University of Minnesota’s Center for Transportation Studies, who has looked at how traffic has moved along the corridor since the freeway’s reconstruction in 2010 and enhancements.

Among the most revealing findings published in his study, “Congestion-Reduction Measures on I-35W: How Well Do They Work?,” is that drivers are largely ignoring the Smart Lane technology.

The digital signs spaced every half-mile post advisory speeds to warn motorists of congestion or traffic issues ahead, and suggest how much to slow down. The idea is to spread the traffic out and get drivers to ease into congestion instead of slamming on the brakes at the last second. It also is designed to reduce the number of rear-end collisions.

“Surprisingly, people don’t obey, and the system didn’t work as intended,” Hourdos said. “If they obeyed, congestion would be reduced. It’s easier to go 40 miles per hour for 10 miles than to go 60 miles per hour for seven miles and 30 for three miles. That is a collective decision.”

In England and Germany, where Smart Lane technology is used, studies show a 30 percent decrease in collisions and a 22 percent increase in roadway capacity. Motorists there can get tickets for not following the speeds posted on the digital signs. “They observe them and they see less congestion. We are not getting the full benefit.”

Hourdos also found that congestion eased slightly when northbound Metro Transit buses stayed in the MnPass lanes longer after departing the 46th Street Station, which is in the center median. After stopping at the station, buses often leave the MnPass lane immediately and traverse several lanes of traffic to get to the Lake Street stop, which is on the right side of the freeway. The study said commuting time could be improved if buses began their lane changes closer to 38th Street, thus maximizing the benefit of the HOT lane.

To help, Metro Transit and MVTA buses no longer stop at Lake Street from 7 to 9 a.m. A better solution, Hourdos said, would be to move the Lake Street stop to the center median. That is an idea being considered as part of the I-35W Transit/Access project, which includes redesigning the area from approximately 32nd Street to I-94.

The bottom line is that something needs to be done with the ramp from 35W to westbound I-94, where traffic stacks up and spreads backward onto 35W.

When the Crosstown was redesigned, “you took one knot out of the system,” Hourdos said. “Unfortunately, the next bottleneck is downtown because nothing has changed north of Lake Street.”

Follow news about traffic and commuting at The Drive on startribune.com. Got traffic or transportation questions, or story ideas? E-mail drive@startribune.com, tweet @stribdrive or call Tim Harlow at 612-673-7768.

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