For road repairs, closing highways vs. limiting traffic

Drivers in the Twin Cities metro area can look forward to a little relief, as Interstate 94 between Minneapolis and St. Paul is reopened to traffic. I-94 has been closed sporadically on weekends for two construction seasons as improvements were made.

The I-94 closure over the weekend caused miles worth of traffic tieups, and some people question the value of closing roads completely during construction, rather than just limiting traffic.

People at the Minnesota Department of Transportation planned that closure of eastbound I-94 several weeks ago. But closing a freeway completely was once considered a radical thought.

"The thought was, 'You can't shut that down; you have to keep traffic moving. The public won't accept it.' We found out that's not true," said MnDOT engineer Tiffany Dagon.

The first time Dagon remembers closing a major road was 2007 -- and it was Highway 36. MnDOT chose to shut the road entirely for five months instead of blocking off a few lanes for two years, Dagon said.

"Before the project there was market research done, and it was pretty split 50-50 on full closure versus two-year construction and keeping the road open," she said. "After the construction was done, they did research again and found that 90 percent of the respondents were happy with the closure and preferred that to the two-year option."

Dagon said drivers also respond well when they learn full closures are cheaper, because construction crews don't have to spend time every day setting equipment up and getting it back in the right place.

But closures do lead to detours. MnDOT tries to route detoured traffic to other state roads. When traffic is sent to county or city roads the state has to compensate those entities.

The recommended detour is often the quickest route for people on long-distance trips, but not for people going short distances, said MnDOT's Tom O'Keefe.

So that's why and how they close roads -- but why do they do it so often? It's partly because there are more road projects now than ever before.

"Much of our interstate freeways, which carry the greatest volume of our traffic in Minnesota in the metro area, were built in the '60s and '70s," said O'Keefe. "So they're coming due for replacement now."

There are those who ask if all of this is necessary. David Levinson, a civil engineering professor at the University of Minnesota, points out that once a road is closed, it's cheaper to get as many repairs as possible done.

On the I-94 project, for example, MnDOT didn't just increase capacity. It used the opportunity to upgrade the drainage system, even though it might not have been at the point where it was absolutely needed.

"The question is, are our standards too high?" said Levinson. "We demand that lanes be certain widths and we demand that pavements be certain thicknesses, and drainage be certain ways -- which are really all nice things to have, but are also costly. And the cost is not just the money spent, but the delay and people who suffer through the construction process."

Road improvements have to be done sooner or later, MnDOT's Dagon pointed out. She said she hopes people trust the decisions she and her colleagues make.

"One thing I'd want people to know is we work really hard to meet people's needs," she said.

The next big metro area project coming up is I-35E north of downtown St Paul. Dagon's group at MnDOT decided against closing it to replace bridges and an interchange, because they found the displaced traffic would put too much of a burden on other roads. Instead, beginning in 2014, traffic will squeeze through a construction zone.

The work on that stretch of highway will take about two years, and the improvements will last about 35 years, Dagon said.