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Speaking of city planners, you can always call them to complain about a particular intersection. They will do a traffic study to determine if any changes need to be done. I did that once long ago in Austin.

But in general the systems are quite limited and set up (in a flow with other lights nearby) for peak times of the day such as rush hour. Most intersection lanes have the sensors in the roadbed. I don't know why they can't improve flow and have hourly configurations for lights. I have a complex intersection near the house that includes 2 rail crossings. When a train comes the lights are aware and change their normal cycle to a pretty workable solution (some fast people trains, some slow freight). So I know they can do it. Maybe it's just cost. Plus most people are just sheep and never complain, and gov't won't do anything until you poke them with a sharp stick.

I live in the suburbs of NYC called Westchester County, north of the Bronx and south of the Putnam County line. Anyhow, the suburbs we all see pictured in the movies with little traffic and pristine silence is no longer the case. The amount of traffic has increased exponentially, but the roads and traffic lights are still programmed for 1950s' traffic volume. Just recently, after a long running complaint from area residents, the town expanded the left turn lane of a major intersection because soutbound cars waiting to make a left turn on Rt 100 (Central Ave) onto my street were waiting on the diagonal yellow lines (commonly used by highway patrol to clock speeders) in the middle of the two way street because of the volume of traffic ahead of them. It would take about 5 or more minutes to make a left turn because the separate left turn light also had a very short duration and you had to wait again until the traffic ahead of you makes their turn. It's simply nuts to think that traffic engineers are so out of touch with modern traffic paterns and the need to revamp the entire traffic light system. Granted, the yellow lights stay on longer in the suburbs, giving you more time to cross the intersection without running through a red, but that's not the case within NYC. The yellow lights come on for about 3 seconds and before you know it, the light turns red, causing many drivers to run a red light. The NYC police take advantage of this stupidity by pulling over drivers and ticketing them for running red lights, or they set up them red light photo cameras to snap a shot of your license plate and mail you the ticket. When the light turns yellow, you are practically forced to make a split second decision to either go through the light before it turns red, or to slam on your brakes, risking the possibility of getting rear ended. I can't tell you how many times I see people slamming on brakes at a yellow light, only to get an SUV plowing into their back seat. This entire issue is stupidity in itself and I'm surprised that the city doesn't recognize it as a safety harazard to both drivers and pedestrians.

One of the most useful signals I have seen is a flashing double yellow light installed about 200 feet BEFORE the intersection. When the intersection light is about to change from green to yellow to red, the flashing yellow light is turned on. I discovered that they are timed such that, if you SEE the light start to flash, there is NO WAY that you can get through the intersection without running the red light (or really speeding). The 200 ft. distance to the intersection allows plenty of time to slow down safely for the soon-to-be-visible red light.

But nowhere in the United States that I can recall. It would be a lot more useful to have a warning before the intersection that the light is about to change, but I don't expect to ever see it in this country.

Actually, I see this benefit fairly frequently here between Baltimore
and Philadelphia. However, at least for now it is used almost
exclusively on blind intersections, where you would never be able
to safely stop if you were travelling at the speed limit before
seeing the light. (Of course, how many people are actually doing
the speed limit or less on the average?)

in canada. I've seen them in BC, NS, Que, and of course Ontario.
They are particularily helpful in locations where the traffic light isn't visible from a distance, like over the crest of a hill.

They are usually installed in areas where the posted speed limit is 55 mph or higher, and they work exactly as you describe. The spacing here is slightly longer (about a quarter mile) and the lights actually start flashing before the signal changes to yellow. If you see the warning lights begin flashing and are not already moving at least 10 mph faster than the speed limit, you might as well take your foot off the gas and begin slowing down now.

Unfortunately, the implementation is not consistent from intersection to intersection, even within jurisdictions. In one town, the warning lights at one intersection start flashing when the signal is about to change; at another intersection in the same town, the lights flash continuously.

but the distance back is determined by the speed limit on that stretch of highway. With a 60 MPH road, 200 feet is about 2.5 seconds... not nearly enough time. Our district shoots for an 8-10 second warning, and sets the warning sign at the appropriate distance for the posted speed limit. There are a few places where there would be two traffic lights within this distance (the warning for the second light would be before the first traffic light). In those cases, they decided to synchronize both traffic lights to turn red (and green) at the same time.

On one stretch I travel regularly, the pedestrian lights change green to red a few seconds before the traffic light changes green to yellow. Great for letting drivers know they can keep rolling without worrying about a yellow, or need to zoom to avoid the yellow.