Why are Germany’s roads better? Or are they?

Even roads built to the specifications of Germany’s vaunted autobahn would be challenged by Michigan weather. (courtesy photo)

The question comes up often: Why are the roads in other countries – say, Germany – so much better than those in Michigan?

The Michigan Department of Transportation decided to find out. After studying highway designs in Germany and Austria, MDOT and the Federal Highway Administration in 1993 built a one-mile section of northbound I-75 in Detroit using the more-costly European specifications. For comparison, it built a stretch south of that in the usual Michigan style.

The European section was built with two layers of concrete, thicker than the one layer typical of Michigan highways. The concrete rested on a deep base of a crushed limestone, rather than the sand usually used in Michigan roads. Joints were closer than in the typical Michigan design, allowing for more expansion.

Within two years, both sections had superficial cracks. Twenty years later, “there is no clear indication as to which pavement section will eventually achieve the most cost-effective service life,” an MDOT study said. It noted, however, that the European section was showing signs of wear, with some of the concrete surface “delaminating,” or separating, possibly due to water freezing and expanding, the same destructive cycle that plagues Michigan’s roads.

Since the European section cost more than twice as much, MDOT officials doubt it’s worth building Michigan’s roads in that style. “We can’t afford to build them that way,” MDOT Director Kirk Steudle said.

And it is unlikely Michigan’s taxpayers would be willing to bear the additional cost. Drivers in Germany pay more than $8 for a gallon of gasoline, much of it due to fuel taxes for road maintenance that are about 18 times higher than in the U.S.

The European experiment has not been for naught. Michigan’s highway engineers are incorporating some of the most cost-effective features of that design as they rebuild sections of state highways, Steudle said.

Within the past decade, MDOT began rebuilding roads on a base of crushed stones and sand over pipes that allow water to drain away, said Nishantha Bandara, a civil engineering professor at Lawrence Technological University. In the Detroit area, parts of the Lodge Freeway and Southfield Freeway, as well as a section of I-96 in Macomb County, have been built to the new standard. The roadway connecting I-75 to the new international bridge in Detroit also is being built in that style, said Bandara, formerly a civil engineer with MDOT.

It’s too soon to say whether those changes will substantially improve the lifespan of Michigan’s highways, but Bandara is optimistic.

Winters, lakes hard on roads

Michigan’s climate and its different soils make road building more of a challenge than in most other states, Bandara said.

The Great Lakes, among Michigan’s finest assets, also are tough on the roads. In a typical winter (and this last one was anything but typical), the lakes are a moderating influence, causing several freeze and thaw cycles, more than in any of the other Great Lakes states, climatologists and highway engineers say.

In West Michigan, the soil is predominantly sand and gravel, which is a better base for roads. In the Upper Peninsula, it is rock and swampland. Mid-Michigan is a mix of sand and clay.

Southeast Michigan, the most densely populated region of the state, is heavy clay, which is the worst base for roads, because it doesn’t allow water to drain away. That’s why a section of I-75 in Monroe County is one of the worst in the state.

“In Metro Detroit, we have this very weak clay,” Bandara said, like toothpaste that never completely dries. “If you build on this very weak clay, the pavement is not supported properly.”

Water seeps through cracks in the pavement. When it freezes, the ice expands, causing the pavement to rise. When the ice thaws, it leaves a void that collapses when a heavy vehicle passes over it. Thus is born a pothole.

Bandara is working on a research project for MDOT, using recycled materials, such as fly ash, a byproduct of burned coal, to stabilize the clay.

From the European experiment, “we’ve learned, we’ve reviewed and we’ve adjusted,” Steudle said. “We’re always finding tweaks to build the roads better.”

But rebuilding Michigan’s roads to the new standards would take many decades, since it is cheaper for MDOT to maintain its roads than replace them.

But “hopefully, you’ll see fewer potholes,” Bandara said.