I've wondered this for a while, but it's since I started using one on a remote, but sometimes busy, bypass that I finally felt inspired to ask.
I'd heard of the idea of Urban Traffic Control before, although I didn't that was it's name.
I don't think that's the case with the one I'm using, as there's not enough other traffic lights in the area to have any sort of linked phasing.
I've only tried it a few times in the couple of days since I asked, but the idea that it is linked to approaching traffic speed sounds like it could be right.
The one time when I pressed the button and there was no traffic in sight, it changed instantly.
I like the idea of the lights being set to red for road traffic and car drivers having to get out to press the button.
More realistically, giving cars an instant red when a pedestrian presses the button, then waiting until the induction loops detect the cars have stopped before giving pedestrians a green light would be a better system. Even more so if it had cameras to record cars running the red light.