DOUGLAS COUNTY — 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) and 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

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