Those black cables stretched across streets, roads and highways that seem to appear annually like flowers in the spring aren’t part of a spy network.

They’re recording data about traffic that help state, county and city planners make decisions about land use, road maintenance, safety and urban growth. Even national companies mine the data in search of information for business decisions.

La Plata County will have a lock on traffic volume along East Animas Road (County Road 250) through the eight traffic counters that Steve Baca placed Monday.

Baca, with the county Road and Bridge Department, installed the counters the length of the winding road that hugs the cliffs beneath Missionary Ridge.

“Counters register date and time and can be programmed to record traffic volume, class of vehicle, speed and weight of vehicles,” Baca said. “The ones today will measure only volume.”

Baca chains the gadgetry-filled counter, which is slightly smaller than a box of Kleenex, to a metal road sign, then secures it again with a spike in the ground.

He stretches the cable taut across the road and spikes it to the ground. A vehicle rolling over the cable activates the counter with a puff of air.

The counters distinguish between regular vehicles and large commercial trucks by the length of the wheel base.

“We put the counters out on Monday and remove them on Wednesday,” Baca said. “I’ll put these somewhere else next week.”

Baca has been the county’s traffic-counter man for almost eight years. Among other tasks, he makes, installs and repairs road signs and drives a snowplow.

Counters are placed to pinpoint volume and source of traffic as much as possible. A case in point: Last week, counters (not the county’s) were positioned at the intersection of Florida Road (County Road 240) and County Road 234 to register through traffic and the contribution of County Road 234 to the overall flow.

Lower-volume roads get attention, too. Baca placed a counter on County Road 254, a no-exit spur off Florida Road where only a handful of houses are visible.

But there’s more than meets the eye, said county project engineer Aaron McKelvey.

“The road generates 399 trips a day – more than I imagined and more than enough to meet monitoring criteria,” McKelvey said. “And there are still some undeveloped lots in there.”

The city of Durango has taken traffic counts for years, applying the information to land-use decisions, creation of Durango Transit routes and installation of traffic-control devices.

The intersection of East Second Avenue and east Eighth Street was made a four-way stop within the last couple of years based on traffic counts. In 2011, the intersection was identified as among the city’s most accident-prone.

The Colorado Department of Transportation places counters on interstate, U.S. and Colorado highways on three-year cycles, said Nancy Shanks, communications manager for CDOT in Durango. In all, counters are placed at 3,310 points.

The data gathered shows traffic volumes that help CDOT schedule work and maintenance. But the counts reveal other information, Shanks said.

Among the tidbits:

The state has 9,103 miles of highway but 23,000 lane miles, which is important for scheduling maintenance and snow clearing.

The interstate highway system accounts for 10 percent of highway miles in Colorado but 40 percent of all traffic miles.

Motorists travel 28 billion miles a year on state, U.S. and interstate highways in Colorado. When county roads and city streets are included, motorists cover 47 billion miles annually.

CDOT counts vehicles to devise specific traffic configurations, Shanks said. An example, she said, is the recently completed overhaul of the Camino del Rio-College Drive intersection.

Westbound College now has five lanes – a right-turn lane, a through lane, a bike lane and two left-turn lanes – but eastbound College has only a bike lane and a single through lane.

Traffic counts determined the number of lanes needed in either direction, Shanks said.

CDOT sends its traffic counts to the Federal Highway Commission. Fortune 500 companies burrow into the data for their planning purposes, Shanks said.

The counters are deployed from April through October, usually on either side of major highways, she said. They’re placed usually on Tuesday, Wednesday and Thursday to avoid peak weekend travel.

McKelvey said the county places counters once a year on most paved roads. They stay in place two days and then are moved.

Counting traffic in the county dates to 1985, McElvey said, but it’s been done annually since 1994.

“Traffic counts help us see trends, determine when maintenance is needed and see how new development affects traffic volume,” he said.

daler@durangoherald.com