I had no idea this was even a thing. According to The Colorado Sun:
The $120 traffic violation, worth four points on his driver’s license, is what the town calls a “citizen-signed complaint.” A person who sees what they think is a traffic violation can call police and provide details after the fact about what they saw — suspected intoxicated drivers, speeding, blown stop signs and traffic lights. Police write up the ticket, but the citizen-witness has to sign the complaint and agree to appear in court to testify, should it come to that.
This recently happen to a man who lives in Colorado Springs while he was driving through Woodland Park. You can read the full story HERE.