MANKATO – Plow drivers know their business. They know what works, and what doesn't.

"It's one thing to intuitively say, 'We've seen it. We know it,' " said Tom Peters, maintenance research engineer for the Minnesota Department of Transportation.

But without hard data, their observations are unlikely to change the practice of plowing.

That's where Minnesota State University, Mankato civil engineering professor Stephen Druschel and his team of undergrads come in. In a series of experiments last winter, they measured the effectiveness of de-icing and plowing methods on contract with MnDOT at a cost of $116,144.

Their task, broadly speaking, was to evaluate the methods and materials MnDOT uses to clear roads of ice and snow, and see if they could be improved, Peters said.

The work followed a 2010 MSU project that examined the effectiveness of 25 types of road salt. Though that earlier work was done in a lab, the second phase moved into the field during what happened to be the coldest Minnesota winter in 35 years.

Druschel said MnDOT and the department's other clients tend to appreciate how students gain experience carrying out the work.

One of the most involved students in this project, Amy Nguyen, is in her fourth semester at MSU.

Like other students, Nguyen received a stipend to do some of the research but now is working more or less as a volunteer.

Evaluating how well different snowplowing techniques and materials work, it turns out, is quite complicated.

Case in point: What's the most effective way to apply a chemical de-icer?

To answer that, the researchers received permission from Valleyfair and Canterbury Park in the Twin Cities to turn their huge vacant parking lots into 1,000-foot-long snowplow test runs.

Even with repeated tests, drawing conclusions about cause and effect, especially ones that can be applied to different roads, can be tricky. Might the angle of the sun have had an effect? The type of snow? The type of pavement?

Drivers had reported that another factor, heavy traffic and especially truck traffic, could improve de-icing. They appear to be right.

During testing at Canterbury Park, car traffic that followed the de-icer truck led to a modest improvement in de-icer effectiveness. The truck traffic led to substantial melting only 10 and 20 minutes later.

Peters said this might mean that for some rural roads it would be worthwhile for the de-icers to be followed by a truck.

But this suggestion, like all the rest, needs to go through the state's maintenance engineers. That's the next step for the study, Peters said, before it can begin to be implemented.