Driving the Diverging Diamond Interchange at Hwy 60 after Oct. 3

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The Diverging Diamond Interchange (DDI) is a new traffic pattern for the Town of Johnstown. While it will provide more efficient and safe travel on Hwy60 across I25, it will also take a moment to get used to. 

What is a DDI? A DDI crosses traffic to the left side of the road across a grade separated interchange (in this case, over I25) and allows vehicles to have direct access to freeway ramps without having to wait at a traffic signal. Vehicles cross to the opposite side of the road at a traffic signal. Left turns at the interchange do not cross oncoming traffic, which results in fewer crashes because there are fewer potential conflict points. Crashes that do occur are likely to not be as damaging as the T-bone crash that can occur with left turns at typical intersections. A DDI configuration is able to move high volumes of traffic through an interchange without increasing the number of lanes and traffic signals.

Additional benefits of a DDI include:

  • Reduces delays using a two-phase signal as opposed to a traditional four or six-phase signal. 
  • Requires fewer lanes but can handle more traffic capacity. 
  • Reduces conflict points at intersections. 
  • Improves pedestrian crossing safety with easier access to medians. 
  • Increases left-turn capacity. 
  • Eliminates wrong-way entry to ramps. 
  • Costs less than a typical free-flow interchange utilizing single directional flyover ramps. 

If you drive cautiously and follow all road signs, signals, and pavement markings then you will get the hang of it in no time. Below are a few resources on navigating a DDI. Safe travels!

Diverging Diamond Interchange Video
CDOT's North I25 Project Webpage


Finishing Work on the DDI after October 3, 2022

The DDI will open to traffic after 10/3/2022. There will be some continuing work on the following after that time:

  • Landscaping
  • Irrigation
  • Concrete Work
  • Other aesthetic improvements

When the interchange is fully complete, which is expected in mid-2023, there will be two lanes in each direction with a 10-foot-wide sidewalk, and upgraded landscaping and aesthetics. Upon reopening the interchange in early October, CO 60 over I-25 will be in a one-lane in each direction DDI configuration to finish landscaping, irrigation and concrete work. Motorists are encouraged to use caution after the interchange reopens, as the traffic pattern will be significantly different and construction vehicles will be parked in the closed lanes (shown in red shading below).

A diagram of the trafflic flow on the Diverging Diamond Interchange (DDI) at the intersection of Interstate 25 and Highway 60. In a DDI, the through lanes that cross the intersection flow around a grade separated interchange, crossing to the opposite side of the road at a traffic signal. This allows vehicles direct access to their right-side freeway ramp without having to wait for the light. Left turns at the interchange also do not cross oncoming traffic.



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