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Autonomous track construction saves time, improves profitability

Photo: Trojak Communications

Photo: Trojak Communications

The most often cited reason for a company’s reluctance to move toward a GNSS-based capital equipment purchase is cost. Not so for the Redland Company, which embraced GNSS long ago and employs it in almost every facet of its operation.

On a unique 475-acre Florida Department of Transportation (FDOT) project, Redland used millimeter-grade GNSS on a Gomaco 9500 trimmer to final grade a 2.25-mile oval track, saving months over traditional string line grading. For Redland, the solution has gone from a necessary expense to an entirely new profit center.

The FDOT SunTrax project includes construction of a proving ground for autonomous vehicles. When complete, the 200+-acre center will offer a test chamber to simulate weather, an area where pick-ups and drop-offs can be replicated, and a precision-graded 2.25-mile oval test track.

The oval is designed to replicate turnpike travel at 70 mph. “Because FDOT had some very strict tolerances on the track surface itself, the grade had to be extremely precise,” said Walt Thomas, Redland’s division superintendent for grading/trimming operations. “So when we got out here, all the rough grading had been completed and we were brought in to prepare it for the asphalt course.”

Neatly trimmed

Photo: Trojak Communications

Photo: Trojak Communications

For ultra-fine grading, Redland uses a trimmer/placer that offers advantages over a motor grader, including an ability to resist “floating” over higher density material or cutting into lower density material. To maintain grade, trimmers typically are used in conjunction with a string line which, while effective and accurate, is also labor-intensive, time-consuming and challenging.

Because of the project’s size, Redland has used Millimeter GPS from Topcon Positioning Systems on its Gomaco 9500 for more than two years. “We have gotten tremendous results with it,” Thomas said. “We knew that, for here, it was the only viable trimming approach.”

Redland’s Millimeter GPS uses a series of tripod-mounted Topcon LZ-T5 laser transmitters placed at an established reference point to generate a 33-foot-high Laser Zone signal. That signal is accessed by the receiver on the trimmer and used to determine elevation, set the necessary depth of the trimmerhead, and maintain the required tolerances.

While most of the project only needed two lasers, four were used for the curved sections of the oval track, including a turnaround loop for testing larger autonomous vehicles like semi-trailers. “Trimming anywhere from 1 to 2 inches of material, we were averaging rates of about 800 square yards per day — and the accuracies have consistently been dead on,” Thomas said.
The machine running the millimeter-grade system is in steady demand by many of the area’s premier grading contractors in Florida and North Carolina. “For us, it has paid nice dividends,” Thomas said.

Comfort in 3D

Topcon equipment that Redland Company used for the SunTrax construction included the 3D millimeter system, the Topcon HiPerV base and rover, laser units and FC-5000 controllers, purchased through Lengemann Corporation in Altoona.

For Redland, Topcon GNSS solutions “have been great for our own operation and a powerful solution to offer as a subcontractor,” Thomas said. “We are getting to a point here in Florida where having a 3D capability is almost a prerequisite for bidding many jobs. No problem, we are already there.”

The SunTrax facility is being jointly developed by Florida’s Turnpike Enterprise (FTE), Florida Polytechnic University and industry partners. The cutting-edge facility, which will offer unique opportunities for testing emerging transportation technologies in safe and controlled environments, is being touted as the only high-speed autonomous vehicle testing facility in the southeastern U.S.

SunTrax is slated to open this year.

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