CDOT puts pacing program in gear on I-70 mountain corridor
December 20, 2011
It seems almost counterintuitive: slowing down cars to speed up traffic.
But that is the plan the Colorado Department of Transportation put into action Sunday starting up its new pacing program on one of the first peak ski weekends of the season.
CDOT launched the program officially for the first time Sunday, controlling traffic speeds through the frequently congested Interstate 70 mountain corridor from Silverthorne all the way to Floyd Hill, where the highway widens to three lanes.
Results of several tests of the program indicate keeping cars moving at a slow, but steady speed on peak Sunday afternoons prevents backups and actually shaves minutes off the drive time, CDOT officials said.
The pacing program, also called rolling speed harmonization got under way just after 11 a.m. Sunday as traffic hit 1,900 cars per hour through the tunnel and ran 12 miles further than the most recent trial, which tested the program through Empire Junction.
“Once we removed ourselves the last time, when we just went to Empire, that’s when we started seeing … traffic slow down significantly,” Wilson said. “So the decision was made to go further with this and we’d probably maintain a more harmonized speed all the way to the bottom of Floyd Hill.”
How to pace a packed highway
A total of 24 law-enforcement officers in marked patrol vehicles from the Silverthorne Police Department, Colorado State Patrol and Clear Creek county participated in the pacing Sunday. Authorities split the 39-mile corridor into short sections, with patrol cars from the proper jurisdiction pulling in front of traffic every few minutes, lights activated, and controlling speeds.
CDOT officials compare the process to draining water through a drain or funnel. If poured too quickly, a large quantity of water will get backed up and take time to drain, but if poured slowly, the water will flow through smoothly.
Pacing is only really effective, however, when traffic volumes are at approximately 1,900-2,300 cars per hour through the tunnel. On some Sunday afternoons, traffic returning to Denver can get 3,000 cars per hour through the corridor.
CDOT officials say they are constantly reviewing the process to ensure it is working effectively.
To run the pacing program for a single Sunday afternoon costs the transportation department between $4,500-$5,000.
CDOT pays for off-duty law-enforcement officers to run the pacing operation and for the patrol vehicles used for the program.
The speed harmonization program was originally envisioned as a way of reducing metering on I-70. Metering causes cars to be stopped for up to 20 minutes on the west side of the Eisenhower Tunnel while traffic filters through. It is used to prevent gridlock inside the tunnel, which would block first responders’ access in the event of an emergency.
“The traveling public is not real fond of metering and stops,” Wilson said. “So if we can reduce that somewhat, then I think that’s a win for everybody.”
Pacing is expected to reduce, but not eliminate, metering this season.
The pacing program was also intended to keep traffic flowing smoothly, though slowly, on the 10-mile incline from S’thorne to the tunnel, where the stop-and-go effect causes rear-end accidents and cars to get stuck on the often icy, slick or snowpacked highway.
The pacing program will continue to run on eastbound I-70 on Sunday afternoons and some holidays as needed through March or April, CDOT officials said.