Currently, when metering is under way, the CDOT stops all inbound vehicles from entering the tunnel when traffic is backed up due to safety concerns for periods of 15 to 20 minutes or more. The road has no shoulders in the tunnel, and emergency vehicles must be able to get through when traffic is at a standstill.
Instead of just stopping all traffic, CDOT will be trying a new method of metering traffic. This method is used in other states such as California and New Jersey. This method is similar to the highway entrance ramp metering method used in the Denver metro area and other congested areas.
When metering becomes necessary, as traffic approaches the tunnel, it will be spread into four lanes with traffic signals located above each lane. The traffic signals will be used to alternate lanes of traffic in an effort to more efficiently regulate the flow of traffic into the tunnel. The traffic signals will cycle every 4 to 8 seconds so vehicles will only have to stop briefly before being allowed to enter into the tunnel.
CDOT hopes this continuous flow metering with only brief stops will reduce the delays caused by traditional metering. For every minute traffic is stopped for metering, it can take as much as eight minutes to get the backed-up traffic moving again.