red light ones are not great due to increased rear endings from some idiot slamming the brakes on when they should have gone through / people rushing and assuming the person in front will go through the yellow.

speed ones work great, when placed appropriately (i.e. on a street with an appropriate speed limit for the road design and in areas of higher pedestrian activity). I hate that Ontario just banned speed enforcement cameras, because that means a loss of revenue to pay for the road network maintenance, more police activity enforcing speed (which a camera does automatically all day long) which means police aren't doing more important stuff and also it's a waste of my tax dollars, and they will have to spend more of my tax dollars putting shittier speed reduction methods in place like speed bumps (annoying as fuck, bad for fuel economy, loud because people race from speed bump to speed bump, ineffective because people pay attention racing from speed bump to speed bump instead of to what's going on around them, annoying for bicycles and people with towing trailers, loud when people telling trailers go over them, loud when regular cars go over them, bad for snow plows....)

now, this is just for speed enforcement, not coordinating traffic flow. although in a properly designed network, there are times that this can actually be achieved, unlike those light cycles on arterial roads that let you go through if you speed just a little bit but if you go the speed limit you hit every single red light