Associated Press
04-13-07
GPS guided road construction cuts costs and time
As the road construction season kicks into high gear, Minnesota will continue to
experiment with a high-tech way of guiding the bulldozers and other machines
building the state's roadways.
Minnesota will use global positioning satellites in "machine control" construction,
a new way of road-building that promises to speed construction and create
longer-lasting roads. The use of GPS to build roads is just beginning, but it's
likely to expand in the five years, said David White, a geotechnical engineer at
Iowa State University, which offers a class on machine control construction.
"It's a huge change," he said.
In machine control construction, machine operators use GPS signals and an
onboard computer with a 3-D view of the project, so they "don't waste time
moving material that doesn't need to be moved," White said.
The Minnesota Department of Transportation is hoping that using the technology
on the Highway 36 project in North St. Paul this summer will help the project run
more efficiently. The experiment will scatter 40,000 daily users of the road to
alternate routes, and MnDOT is watching to see how lower costs and shorter
construction time balances against the disruption.
Britton Lawson, who has used GPS, said he would never go back to leveling
roadbeds by following marks on wooden stakes pounded into the ground by a
survey team.
"I don't have to wait for a staker to come out and give me grades," Lawson said.
"You can move dirt right the first time."
Machine control construction isn't cheap. The equipment adds about $60,000 to
the price of a bulldozer, and about $80,000 to the price of a compactor.
Contractors must also spend about $50,000 for a base receiver station, which
can be used by multiple machines.
But contractors are willing to pay because the machines speed up work and cut
construction costs, said Bill Hines, grading division manager for Progressive
Contractors of St. Michael.
"If I think I can do it 10 days faster than my competitor," he said. "I don't have to
put those dollars in my bid."
The new technology is "kind of unbelievable," Hines said. "In the old days
surveyors would give you cuts and fills on a piece of wood. They might write 'Cut
3 feet,"' Hines said. "Now the machine is able to sense those cuts or fills. It's
exciting for all of us."
GPS-guided earth-moving has been in use on some highway projects in
Minnesota for several years.
Machine control is not perfect, said Lou Barrett, MnDOT's transportation program
supervisor. It's best suited for big jobs that require earth moving.
Progressive Contractors landed the $27.5-million Highway 36 contract, partly
because it has the timesaving machines, Hines said.
The International Union of Operating Engineers Local 49 has been training union
operators in satellite-guided construction equipment for three years.
"Pretty soon every piece of equipment out there is going to have a GPS on it,"
said Michael Gillson, a GPS instructor for the union. "I have guys that even
halfway through the day say, 'I don't know why anyone would want to do without
it.' "
(Copyright 2007 by The Associated Press. All Rights Reserved.)