All traffic runs in the same lanes: auto-guidance keeps equipment on precise paths.(Production)

Harlan Downing has turned into a real traffic cop in his Colby, Kan., fields. That's because he holds his field operations to a new set of rules: all machines have to run in the same tracks--and they have to do that one season after another.

The new rules put Downing on the road to controlled traffic--with the promise of less compaction and better yields. Sub-inch auto-guidance, strip-tillage and equipment modifications make it all possible.

Controlled traffic with tramlines for field traffic has intrigued engineers and agronomists for years. "You can control wheel traffic without a guidance system, and a few no-till farmers do," says Ohio State University (OSU) Extension agricultural engineer Randall Reeder. "But it's much more difficult."

The advent of guidance systems using a real-time kinematics (RTK) satellite signal--which provides sub-inch accuracy that is repeatable year after year--could lead other farmers to follow in Downing's footsteps. "I'm convinced the next yield breakthrough will result from controlling traffic," says Dean Wesley of Key Agricultural Services. Two of this Macomb, Ill., consultant's clients are considering moving to controlled traffic.

Downing started the controlled traffic process by switching to strip-tillage for his irrigated and dryland corn, soybeans, wheat and milo. He soon found that strip-till required the precision of RTK auto-guidance.

"The first year I strip-tilled, I used row markers," he explains. "When I planted, I discovered I had drifted with the strip-till bar. I got a more even stand and better rooting whenever I planted exactly over the strip."

On top of that, residue drifting back over Downing's strips or captured in the mound by the closing disks, made the strips difficult to see when Downing began planting.

Besides adding a Trimble AgGPS Autopilot …