Sir Xsarus wrote:
gbaji wrote:
This is how sensor based signal lights work. Do people not actually know this?
Did you read my second post? It's not generally how sensors work.
Yes, I did read it. I just disagree with your conclusion. And your statements don't really support your conclusion anyway:
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1) The extend the green light idea applies to minor streets crossing larger streets. The idea is that the smaller street will generally have a shorter light, but in the event there is an unusually large number of people it will extend the light by a small amount. Certainly not infinite, and the context is backed up traffic, not fast moving traffic on a main street.
This is you basically agreeing with me. Unless you have some alternative explanation as to how lights managed to detect "backed up traffic" other than being able to sense when cars are in a continuous unbroken line (which is *exactly* what I've been talking about). This is why I've been talking about "gaps" and not "speed". You don't speed up because going faster makes the light stay green. You speed up to catch up to the car in front of you, so that the sensor sees you as being in one unbroken line of cars with that car. Once someone leaves a gap, the light will change.
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2) Most intersections wouldn't have this, and will just use sensors to trigger the aforementioned minor street, or to trigger a turning light.
Most is a relative term. So "some" do, right? So there's no harm in closing the gap between you and the car in front of you, just in case, right? If a light has sensors at all, there's little reason not to have it programmed to detect traffic density when making cycle decisions. Programming is cheap. Making the lights smarter saves massive amounts of money.
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3) there are fully automated intersections that monitor continuously, and certainly there could be a case where both streets are monitored and could be extended either way, but it would be rare and not worth closing a gap to do.
And here you acknowledge what I'm talking about, but then claim it's not worth closing a gap. Um... Why not? And how would it be "rare"? What exactly do you think a fully automated intersection is doing? So we fully automate everything except the ability to detect the flow of traffic to determine whether to change the light? That seems like "not really automated at all". What conditions do you think a "fully automated" light should use to make cycle choices? I'm honestly curious here.
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This is sourced from the traffic planning and infrastructure development of SF for reference, so it's not like I'm just making it up because I talked to a civil engineer once, or observed roads as I drove along them.
It's sourced? Then source it. Saying "this is sourced" doesn't mean anything. Doubly so when what you are saying directly contradicts direct observations I make virtually every single day. There's a light at an offramp/intersection I drive every single day. That light will stay green a very very long time (because one side is an offramp from the freeway), but only as long as traffic continues to flow unbroken up to the light. If there's a gap, it will change to yellow immediately. This is trivially easy to test. All I have to do is slow down to allow a few extra car lengths between me and the car in front of me than I would normally set and the light will change to yellow as I'm approaching. You can literally see that once the gap between two cars hits that sensor (well, a car fails to cross the sensor in a given period of time), the light will change. Every. Single. Time.
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I thought your description sounds interesting, if unrealistic from my admittedly limited knowledge from a few civil engineering classes so I investigated further.
Then link your investigation. Again, I can get in my car *right now* and within 10 minutes directly observe this behavior. Maybe it's different where you live, but this behavior is common around here. I see it every day. And not just at that one intersection. I see this at lots of intersections all the time. I see a gap between cars crossing the sensor and I see the light turn yellow. All the time. It's how lights around here have worked for years. If the lights are on sensors at all (which most in San Diego are), they tend to exhibit this behavior. Cause, why not? It's a smart way to operate your lights.