I have no idea where in Los Angeles this photo was taken, but that’s beside the point. It’s a wonderful close-up of the semaphore traffic lights that controlled L.A. traffic until the three-light signal replaced them in 1956. The La Salle and Buick in the background dates this photo to circa 1928. But two things I had never noticed about semaphores before is the third, smaller light at the bottom. Can anyone tell me what that was for? And that box on the pole—was that used to adjust or fix the light? It kind of looks like one of those call boxes used to contact the police or get a taxi. I’d love to get some confirmation about what it actually did.
Susan M said: “The bottom, smaller light was a yellow light indicating caution. They usually were a flashing yellow in Los Angeles. The box contained the wiring/controls for the signal. They needed adjusting often.
You also used to see flashing yellow lights after say 9 or 10pm at some intersections. This was an indication of lower your speed and proceed with caution, knowing there might be multi cars with right of way in the intersection. Never made much sense to me to have a flashing yellow intersection in the later hours of a typically slower intersection vs just use the signal lights in an ongoing manner. Before all railroad crossings had cross guard arms that raised and lowered, some had yellow flashing lights to indicate proceed through the crossing with caution. Those are the main things I can recall about the old Acme and other automated signals that flashed yellow. Not all the Acme signals had a yellow light by the way. You’d run into some of the older ones put in pre-mid 30s that only had the red green lights. Most of the busier traffic areas replaced those however with the ones that had the little yellow bottom light. I can remember some of the old red green lights left for years however. Areas out by Mine Fields/LAX, down into the outskirts of Torrance, Gardena areas didn’t change out to newer signals until post war. Then those were retired lickity-split for the red-yellow -green lights that are more typical of those seen today.
On the Acme signals like this one, which is what most of the LA area had from the 30s on, the yellow light flashed before the red light would come on. They added the flashing yellow lights to cut down on running red lights by accident. In LA on a flashing yellow light, we could proceed into the intersection with caution, same as a green light. Some areas of the country, laws were different, and a yellow light meant almost the same as a red light. If the intersection was compromised by an accident or road work, the cops or roads dept usually turned the the signals for the intersection to flashing red for a 2-3 or 4-way stop. The only time you usually saw the flashing yellow was about 30 seconds before the signal changed to red. The timing sequence could be altered based on traffic patterns and how large the intersection was. Before all the meters in the streets and cameras in the sky, we used to have road dept employees called traffic counters! They sat at intersections (at the curb), and collected stats, timed signals and counted cars.”
Andie P said: “There were often older, usually deskbound cops who directed traffic at intersections when there was an accident – or a water main break, which happened once when I was with my stepmother in Hollywood. The cop arrived on a bicycle! Opened the box and set it to 4-way stop. The box on the pole could be accessed by Police or Fire to call in problems and also to SET the signal to ALL STOP, like the flashing red lights we have now. Drivers were expected to come to a full stop and wait until a TRAFFIC DIRECTOR waved them on, sent them down the side street or made them do a U-turn and go back the way they had come.“
Chris S said: “The Acme traffic signal operated normally during the day flipping out its Stop and Go along with the red and green lights, respectively. The amber light at the bottom would not operate until night. It would go into flash at night. With fewer cars on the road, the timer would tell the arms to “park” themselves inside the signal and the bottom light would start flashing. The next morning, the amber light would stop flashing and the arms would start their waving at traffic again. The box in the post contained the signal controller and timer along with manual police controls.”
The small light at the bottom was used at night for flashing operation, where the signal would flash in all directions.
The box is the controller with the electro-mechanical timing gears that govern the green and red cycles.
Would it flash all the time, John? Or in emergencies?
Martin–It would generally flash at night, say from 10 PM to 6 AM. It would flash yellow for the main street and red for the side street, or all red flash if at the intersection of two main streets. This was intended to reduce delay when there was light traffic and few pedestrians.
Thanks for clarifying that mystery!