>No system can make sense of these requests, and the traffic has to flow. Makes sense to just go through the movements and ignore the buttons. //
One may not be able to mathematically ensure optimal operation but you can certainly "make sense" of the requests.
Surely you read the inputs and only include the pedestrian crossings in the lighting sequence if the buttons are activated. Unless you're halting the traffic for some ulterior flow management need.
As for non-interrupt raising buttons - the "WAIT" light should show to indicate the button isn't required to be pressed.
Lastly, some crossings in the UK have what appear to be cameras (I assumed some form of wide angle IR sensor) facing the pedestrians. I assumed these could provide input as to density of pedestrians waiting in order to balance flow of pedestrians vs. road traffic. Anyone know certainly what they're for?
Responding to the last part of your comment the sensors are there to cancel the crossing request if the pedestrian crosses early or wanders off elsewhere, to avoid stopping traffic for no reason. The sensors pointed at oncoming traffic can be used to halt traffic if they detect it's moving too quickly for the area. Crossings with the sensors and the don't walk/walk lights on the side closest to you are puffin crossings. The other ones are the older pelican crossings. Infos from http://en.wikipedia.org/wiki/Puffin_crossing
"and only include the pedestrian crossings in the lighting sequence if the buttons are activated"
That works for a pedestrian crossing, but not where we have two lanes of cars crossing.
Or if you think in more complicated crossings like O'Connell Bridge in Dublin, there's probably no way the buttons could have any input in the lights there without messing the traffic.
Not sure what the cameras you mentioned do, maybe it's the usual "Big Brother" cameras
Some crossings here, UK, have turn filters; some have full pedestrian access (ie diagonal crossing of a crossroads is enabled). Whilst it's possible to have a sequence in which some roads necessarily have halted traffic usually on single carriageway roads [one lane per direction] it's still an optimisation to ignore the pedestrian phase of the sequence.
One may not be able to mathematically ensure optimal operation but you can certainly "make sense" of the requests.
Surely you read the inputs and only include the pedestrian crossings in the lighting sequence if the buttons are activated. Unless you're halting the traffic for some ulterior flow management need.
As for non-interrupt raising buttons - the "WAIT" light should show to indicate the button isn't required to be pressed.
Lastly, some crossings in the UK have what appear to be cameras (I assumed some form of wide angle IR sensor) facing the pedestrians. I assumed these could provide input as to density of pedestrians waiting in order to balance flow of pedestrians vs. road traffic. Anyone know certainly what they're for?