I-25 South Gap: Monument to Castle Rock

I-25 South Gap: Monument to Castle Rock

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The Gap is an 18-mile stretch of Interstate 25 from Monument to south of Castle Rock, connecting Colorado’s two largest cities, Denver and Colorado Springs. Tolling on these lanes began in 2024.

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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HOV3+ users must have an ExpressToll account, a Switchable HOV transponder set to “HOV” mode, and three or more people in the vehicle to use the Express 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.
  • 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.