Sir Xsarus wrote:
The idea of closing a gap to prevent a light from changing is most likely only going to occur in a situation where a light has quite recently changed on a side street with a fair amount of traffic backed up behind it.
A high percentage of lights where I live are configured to do this. It's rare to see a light that *doesn't* exhibit this behavior. It's not just to deal with one scenario, but to more intelligently manage the lights in suburban areas, where the intersections are "busy" all the time, and traffic patterns may change in ways that aren't easily correlated just to time of day (as they may be in a more grid like downtown configuration).
The point of this type of system is to ensure that the traffic lined up and waiting for the light can go (again, barring someone not noticing the light changing), but that once that first group has gone through, it will immediately change if the following conditions are met:
1. There is traffic on any other sensors waiting at their light (which is going to nearly always be true).
2. There is a gap in traffic on the light that is currently green.
Additionally, once some predetermined amount of maximum-green time has passed, the light will change.
This is how nearly every single light near where I live works. Again, maybe it's different in SF, but I can see this behavior every single day on lights everywhere I drive. The fact that it's so ubiquitous around here is why I'm so surprised by the "that can't be how they work" response I seem to be getting. I assumed that lights everywhere worked like this. Because it's a much smarter way to do things than to just have timers. Why bother with sensors in the road if you don't actually use them to control the lights on the fly?
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This is the scenario these sensors are looking for and are put in place to ameliorate. From my perspective, this means that most lights won't behave this way...
I think your first assumption leads you to that conclusion. Eliminate the assumption and the conclusion no longer makes sense.
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...and I still find it dangerous to accelerate in case you can close the gap enough. It's setting you up to not be able to stop in time if the light changes, or if the person in front of you gets a yellow an decides to stop when he may have been able to go through, you're accelerating towards him, and it puts you at greater risk.
If you are close enough to the other person that this is remotely dangerous, then you are close enough that you don't need to speed up in the first place. I'll grant you that if you wait until the last second and then accelerate to a high rate of speed to close that gap, you're being dangerous. But my whole point from the start of this discussion was the idea of looking ahead down the road and making easy minor adjustments to speed in order to avoid problems later on. I'm talking about noticing ahead of time that this condition is going to happen and adjusting your speed to close that future gap when it's completely safe to do so. If you're waiting until the last car in a line has just hit the sensor and then flooring it to get on the sensor before the light trips, then yes, you are being dangerous. But that's not what I'm talking about.
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why are you so far behind to begin with?
Um... Because some of us live in a world where every car on the road isn't gridlocked with the others. You turn onto a main street from a smaller side street. A line of traffic 5 cars deep has just started moving at a green light 300 (or 200, or whatever distance might create a gap) feet ahead. You're free to pick any speed to travel towards that light, but it makes sense to pick the one that puts you right behind the last car in that line at the correct distance so that you form into that line. What I'm talking about is simply being aware of setting your speed properly to avoid leaving a gap. I see lots of people who seem oblivious to the fact that the light will change if they don't close that gap and they'll
slowly accelerate down the road and get stuck (or get the person behind them stuck). Just accelerating a bit faster would make all the difference (and is completely safe)
I'm not talking about nutty speeds here. I'm talking about the difference between a leisurely stroll and a brisk walk. Being aware of what's going on ahead of you and adjusting your speed just a little bit can make a big difference.
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Do you have to speed to close the gap? Given that you were most likely stopped, there shouldn't really be a gap.
You've never turned onto another street? You've never gotten off an intersection and onto a surface street? There are lots of ways you'll find yourself looking at the tail end of a line of cars that are some distance ahead of you. Happens all the time.
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The scenario is where you're coming up to an intersection after most of the traffic has cleared and you accelerate hoping to get through before it changes. That's increasing your risk.
If you wait until the last second, sure. But my whole point is that drivers should recognize this is going to happen ahead of time and adjust their speed/distance well ahead of time when it's still safe. Just like with the scenario I mentioned earlier with the friend who only needed to be aware that the car that just changed lanes might do it again and that it would be prudent to adjust her speed so that if that driver did so, it wouldn't be right when she was next to it. Same deal here. Pay attention. Look down the road. Recognize common driving patterns and their outcomes and make minor adjustments to what you are doing so as to minimize the bad outcomes and maximize the good ones.
I'm not talking about rocket science here. Just a bit of observation and forward thinking.
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I don't know if asking the person who knows exactly what the system does and has helped design it is an anecdote.
The information you get from an expert is a source
for you. It's an anecdote when you repeat that information to a third party. Because I don't know the source and didn't get the information from said source. My "source" is *you*. And you're just telling me something you heard from someone else. A someone else that I have no means to get information from directly myself.
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If you asked me how something I wrote worked, I'd think I'd be the authoritative source.
Yes. Because you wrote it and thus are the expert on it. But if I asked you about something you wrote and then told someone else what you said or meant, that would no longer be a source. It only becomes a source if I point them to you, and they are able to read what you wrote directly.
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I mean you don't have to believe me, but it's not like I asked some random person, or I mentioned talking with a friend who had read an article or something. Take it or leave it, it is still true.
Sure. But from my perspective you did ask some random person. I don't know this expert. You do. Surely you can see how I have no reason to put any more weight in what he said than what you say, because from my perspective you are the one saying it. Point me at this experts blog, or an article he wrote on traffic signals, complete with his credentials as an expert in the field, and now you are providing me with a source. Just saying "I know a guy who said..." doesn't count.
Let me point out, again, that I'm not discounting at all what your friend has to say. I'm just countering that while maybe such lights are uncommon in SF, they are very common in SD. As I've said several times, I see this behavior nearly every single day. It's surprising to me that so many people either haven't seen this, or haven't paid enough attention to notice it. Maybe I'm just more observant than most (actually, I know that I am), but I honestly thought this was something more people would have noticed.
Edited, Aug 26th 2014 2:50pm by gbaji