Emergency Vehicle Signals
We had a red light and the cross traffic had a green, however at the same time there was also a small blue light right next to the red traffic light which was flashing. For several minutes traffic in all directions remained stopped as it appeared that none of us knew what this was all about. There were no emergency vehicles coming through.
What this reader is most likely describing is a set of traffic signals that were responding to an approaching emergency vehicle that never arrived at the intersection. It is possible that the vehicle turned into a driveway or shut off the emergency equipment because there was no longer a need for it.
Traffic signals in British Columbia that include a speaker and pair of small blue and white lights on the crossbar beside the signal head will sense the approach of and grant priority to approaching emergency vehicles sounding a siren with a certain pattern. If you see a blue light, the emergency vehicle is either on the cross street or is coming toward you. If you see a white light, it is overtaking you from the rear.
These lights will flash to signify that the regular traffic signals are in the process of changing to grant the emergency vehicles a clear path. When they are on steady, it means that the signals have changed and will be green for the approaching emergency vehicles and red for all other directions of travel.
Traffic at the intersection facing a red must remain stopped for emergency vehicles to pass. Those facing the green must also stop but do so in a manner that allows free passage through the intersection.
Once the emergency vehicles have passed, the blue and white lights will turn off and traffic signal operation will return to normal.
Approach of an Emergency Vehicle - Section 177 MVA