Analysis from the air

By JOSH NEWTON

TAHLEQUAH DAILY PRESS August 29, 2008 12:20 pm

— Nearly every morning, Oklahoma Highway Patrol Trooper Hank Jenks loads into his Cessna 182 and flies out of the Tahlequah Municipal Airport.
Jenks’ aircraft has a few more gadgets than similar planes, but they all play an important part while he’s cruising at 3,000 feet above the earth’s surface.
The Cessna 182 is only one of approximately 10 used by the state law enforcement agency’s aircraft division to assist in manhunts, an occasional transportation, search and rescue – and, yes, traffic enforcement, which helps make the road a little safer for drivers.
“We have two airplanes assigned to the Tahlequah area,” said Jenks.
Pilots try to work a traffic assignment every day. Drivers familiar with the Tahlequah area know one of the most frequently enforced areas is between here and Muskogee, on U.S. Highway 62.
Most drivers cruise down the highway, never paying attention to the white road markers to the side. These markers are placed every half-mile, or 2,640 feet, according to Jenks, and they help air troopers calculate a driver’s speed.
Here’s one way to do the math: The road markers help determine how many feet a vehicle is traveling per second by dividing the total feet – 2,640 in a half mile – by how long it takes to travel that distance. If it takes 24 seconds, that’s 110 feet per second. Multiply feet per second by 3,600 (the number of seconds in one hour), which turns out to be 396,000 feet per hour. Divide the total feet, 5,280 in a mile, by feet per hour to get miles per hour – in this case, 75 mph.
A document dropped off at the Daily Press by a local citizen claims some road markers on U.S. 62 are between 70 and 76 feet short of a half-mile. Jenks said because the road is not straight, he would have to see how the stretch was measured to get those readings before he could determine if they are marked correctly.
Jenks said he intends to have the markers in question measured, and also noted it may depend on which side of the road the markers were measured, as pilots generally use the east-bound markers to determine speed.
“The way we check speed from the air is pretty much with a chronograph and a set distance,” said Jenks.
A chronographs is, in basic terms, a timekeeping watch. Troopers begin calculating time when a driver passes one road marker, and stop calculating time at the next mile marker, which is a half-mile away. Troopers use the time it takes to get from one marker to another to determine a velocity in feet per second, and break that down to determine miles per hour.
Ground forces work with pilots to test the system between the plane’s chronograph system and calibrated radar guns on the ground unit.
“We try to get multiple speed checks on a person, though that doesn’t always happen,” said Jenks. “We always lean on the side of the public. If I get three different speeds, I’ll give that person a break [and go with the lesser speed]. The speed we give is an average speed over that distance.”
This means, for example, a driver who receives a citation for going 77 mph may have been traveling approximately 75 mph and 80 mph at some point during the half-mile measured by a pilot.
Despite what many people think, pilots don’t simply fly around off the cuff, seeking traffic violators wherever they go. Instead, Jenks said, there’s usually a planned enforcement event, scheduled around the availability of ground forces.
“The troopers on the ground will know we’re going to be there, and we’ll try to get at least two ground units in the area,” said Jenks.
U.S. 62 is often targeted because of the high volume of traffic between Tahlequah and Muskogee. It’s a unique stretch of highway because troopers from both Muskogee and Cherokee counties can be prevailed upon with ease.
“What we do is, we visualize, then check the speed, and call out the information to a ground trooper,” said Jenks. “We’ll keep visual contact with the [vehicle] until a ground trooper has it stopped on the side of the road.”
The OHP uses air forces because it is “a lot easier” to spot traffic violations from some 2,000 feet up, according to Jenks. The angle allows pilots to also spot violations those on the ground may miss, like erratic driving. On an average day, pilots can connect ground units with around 15 contacts per trooper, per hour.
“And we’re pretty undetectable,” said Jenks. “Radar detectors are of no use when we’re 2,000 feet in the air. With us clocking speeds, the troopers on the ground turn off their radars.”

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