State transportation officials said preliminary results of the recent attempt to slow Interstate 70 mountain traffic to keep it free flowing show that the technique of using police “pace cars” is promising.
The Colorado Department of Transportation tested the process, called “rolling speed harmonization,” on about an 8-mile stretch of eastbound I-70 from Silverthorne to the Eisenhower Tunnel.
In that test, from about 10 a.m. to 2:15 p.m. Aug. 13, Colorado State Patrol troopers and Silverthorne police officers put on emergency lights, entered the traffic flow and paced the eastbound traffic at about 55 mph, said CDOT spokesman Bob Wilson.
“The test showed very high compliance,” Wilson said, with only one vehicle trying to pass a police pace car.
The attempt to reduce high fluctuations in traffic speed, which experts say often contributes to accidents and congestion, also seemed to work in the preliminary test, Wilson said.
It kept the average speed of traffic at about 55 mph within “platoons” of vehicles led by police pace cars, although engineers noticed that the average speed crept up to 60 mph at moments just before another police vehicle entered the traffic flow, Wilson said.
Officials also noticed that after the speed-harmonization test ended a little after 2 p.m., some motorists put a heavier foot on the accelerator, with some hitting 70 mph, Wilson said.
“That’s what we’re trying to avoid, the big variation in speed that can create a lot of problems,” he said.
On Sept. 25, CDOT plans to conduct a second test of the speed-harmonization technique, with police pacing traffic along a much longer section of eastbound I-70: 27 miles from Silverthorne to Empire Junction.
If speed harmonization proves to be a successful technique, it will be considered as “another tool to reduce accidents,” Wilson said.
CDOT officials also hope that leveling out the wide fluctuations in traffic speed through the use of police pace cars will help the agency eliminate some of the need for “metering” traffic in the Eisenhower Tunnel.
CDOT meters eastbound traffic through the tunnel when heavy volume or accidents causes vehicles to back up.
During metering, officials stop eastbound traffic west of the tunnel to allow existing backups — inside and east of the portal — to clear.
Speed harmonization might be extended east of Empire Junction if the technique proves to be successful after adequate testing, according to CDOT.
The agency also is looking at other ways to reduce congestion on I-70, including an elaborate plan to expand the bores of the Twin Tunnels near Idaho Springs as a way to smooth traffic flow in that area.
Jeffrey Leib: 303-954-1645 or jleib@denverpost.com
