Colorado Department of Transportation spokeswoman Stacey Stegman said there were too many cars trying to get through the Eisenhower-Johnson tunnels on Sunday. They were too slow for the police pace cars, so the program was suspended at 3:15 p.m.

"Traffic volumes have exceeded our ability to effectively pace traffic," CDOT posted on its Facebook page. "Pacing operations on eastbound I-70 have ceased for the day. Traffic on the west side of the Eisenhower Tunnel is still being metered due to the high traffic volumes."

Under the pacing, or rolling speed harmonization program, officers pull out into traffic at Silverthorne, slow down traffic to a consistent speed, then lead those vehicles to Floyd Hill.

CDOT is currently determining how to improve the I-70 Mountain Corridor. The favored plan now includes six lanes from Floyd Hill through the Twin Tunnels, including a bike trail and frontage roads from Idaho Springs to Hidden Valley, and Hidden Valley to U.S. 6.