Starting later this fall, the Colorado Department of Transportation will begin implementing dynamic tolling — changing rates according to real-time traffic rather than time of day — on two sections of Colorado expressway.

The new real-time toll pricing will affect highway lanes in an 18-mile stretch on Interstate 25 between Monument and Castle Rock. Dynamic tolling will also start on the westbound, 12-mile stretch of Mountain Express Lanes between the Veterans Memorial Tunnel and Empire.

CDOT originally said the new tolling would begin Nov. 1, but later sent a correction that it would begin on an unspecified date later this fall.

CDOT representatives say the tolling shift will not mark a significant change in toll prices from set time-of-day pricing. On the South Gap of I-25, prices vary from $1.50 to $4.75. The Mountain Express Lanes can cost up to $9.

The change will come with traffic patterns that might fall outside of the typical busy and quiet hours for each roadway. CDOT said in a statement that the tolls “may be somewhat higher or lower than drivers have been accustomed to.”

Overhead signs will mark toll prices, which may be adjusted every 5 to 15 minutes. The price a driver pays will be the price they see when entering the express lane, whether or not it has changed during their travel in that lane.

Those without an ExpressToll pass will still have to pay an additional license plate fee.

CDOT says real-time price adjustments will help keep the flow of traffic reliable on these two busy express lane corridors.

“To keep the flow of traffic moving, expanding dynamic tolling to these two corridors just makes sense,” said Piper Darlington, director of the Colorado Transportation Investment Office, the division of CDOT that owns and operates Colorado Express Lanes.

“The South Gap and the Mountain Express Lanes are two of the most traveled corridors in the state, and we want to do everything we can to help keep Express Lane speeds reliable. By transitioning to dynamic tolling and adjusting the tolls based on real-time traffic conditions, we’ll be able to do just that.”

Dynamic tolling was first introduced on earlier this year on the Central 70 Express Lanes. CDOT plans to eventually transition all express lanes in the state to dynamic tolling.

Tolling on the expressways of I-25 in the South Gap began at the beginning of this year. Prices have been tied to the time of day, with historically higher traffic times associated with higher prices. Tolls were waved in a two-year trial period after the express lanes opened in December 2021.

With the new pricing system, the I-25 South Gap Express Lanes will still be remain free to motorcyclists, commercial transit vehicles and vehicles with three or more passengers and a switchable HOV transponder.

All vehicles including motorcycles are tolled on the Mountain Express Lanes.