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Driving You Crazy: What are the different colors for on the tolling traffic signal on the I-25 express lanes?

Sometimes there's a white light, sometimes a blue light

Andrew from Colorado Springs writes, “What’s driving you crazy? Can you tell me what the different colors are for on what looks like a traffic signal at each toll plaza on the I-25 Gap express lanes?"

What are the different colors on the tolling signal on the I-25 express lanes?

By: Jayson Luber

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DOUGLAS COUNTY, Colo. — Andrew from Colorado Springs writes, “What’s driving you crazy? I always enjoy your traffic reports each morning as my day begins. I have a question. Can you tell me what the different colors are for on what looks like a traffic signal at each toll plaza on the new I-25 Gap express lanes? Sometimes I see a white light or a blue light.”

That signal, Andrew, is technically called a Transaction Status Indicator (TSI). It operates similarly to a regular traffic light you see at any intersection. The difference with these signal lights is that they illuminate only when a vehicle passes the toll area. The lights of the TSI are illuminated in various combinations to provide visual information to a law enforcement officer of the status of passing vehicles.

The TSI consists of three lights like the regular red, yellow, green signal. TSI colors, though, are yellow, blue and white.

The White Indicator illuminates when a Single-Occupancy Vehicle transponder is detected. This is what happens when most vehicles pass.

The Blue Indicator illuminates when a switchable HOV transponder is detected. The HOV requirement on Interstate 25 in this area south of Castle Rock is three or more people in the vehicle to avoid paying the toll. If the blue indicator light flashes and a law enforcement officer sees this light come on but there appears to be only one or two people in the vehicle, that officer has probable cause to pull over that driver and issue a citation if there aren’t three people in the vehicle.

What are the different colors on the tolling signal on the I-25 express lanes?

The Yellow Indicator is triggered when the system detects a safety situation and the vehicle with that plate is sought by law enforcement. For example, if the license plate is from a stolen vehicle or the vehicle is associated with an Amber Alert. Again, if law enforcement sees that yellow light illuminate, they have probable cause to initiate a traffic stop.

I asked both the Colorado State Patrol and Douglas County Sheriff’s Office if they have to physically be there watching the indicators to know if a vehicle of interest passes the tolling area or if they are notified by the tolling system. Deborah Takahara with the DCSO told me their traffic unit does not enforce these violations.

CSP Trooper Sherri Mendez told me troopers often position themselves in strategic locations where they can see the tolling transponders and indicator lights, but also visually confirm how many people are in a vehicle.

“These spots are useful not just for HOV enforcement, but also for monitoring speeding, distracted driving, and other violations. So while the lights might signal something, enforcement still depends on troopers being in the right place at the right time to act,” Mendez said.

CSP doesn't track or maintain data on how often troopers are positioned in these areas or how frequently enforcement is tied specifically to a yellow or blue light. I was told that the Colorado Department of Transportation (CDOT) is working on connecting new technology to the vehicle detection system that would be able to automatically alert officers when there is a vehicle of interest identified by law enforcement. The system would send an electronic alert to law enforcement so officers would not have to physically be parked in a place to view the indicator lights and could simply receive an alert electronically if a vehicle of interest was identified by the system. This only works, however, if the driver of the vehicle was using the express lane.

CSP said troopers made 408 traffic stops in 2024 for Driving an Unauthorized Vehicle in a High Occupancy Lane or Driving an Unauthorized Vehicle in a High Occupancy Lane Three or More Times.

Denver7 Traffic Expert Jayson Luber says he has been covering Denver-metro traffic since Ben-Hur was driving a chariot. (We believe the actual number is over 25 years.) He's obsessed with letting viewers know what's happening on their drive and the best way to avoid the problems that spring up. Follow him on Facebook, Twitter or Instagram or listen to his award winning Driving You Crazy podcast on any podcast app including iTunes, iHeartRadio, Spotify, Podbean, or YouTube.