I-25 South Gap: Monument to Castle Rock

I-25 South Gap: Monument to Castle Rock

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This project will build one new Express Lane in each direction of I-25 along an 18-mile stretch known as "The Gap" — south of Castle Rock to Monument. The I-25 South Gap Express Lanes opened with tolls waived for testing in December 2021.

How to Use Express Lanes

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Vehicles with one to two people pay a toll to use the Express Lanes with an ExpressToll account or through a License Plate Toll.

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Vehicles with three or more people must have an ExpressToll account and Switchable HOV transponder to use the lanes for free.


Motorcyclists can use the Express Lanes for free without a pass.


Bus and other transit can travel in the Express Lanes.

Corridor Basics

  • Lanes are open 24/7 for testing – no tolls.
  • 18 miles of Express Lanes from Monument to Castle Rock
  • HOV 3+ will be available with a switchable HOV transponder.
  • Adjustable toll pricing system will be used – prices will depend on the time of day.
  • Overhead signs will indicate current toll prices. Tolls will be collected through the vehicle’s ExpressToll account or a License Plate Toll.