In my experience, the Puffin crossings are setup correctly precisely 0% of the time.

If you are going to pay presumably a lot more money for all of the extra detectors and electronics then they need to deliver 2 things as mentioned by OP: 1) They make sure that anyone on the crossing has time to cross rather than stopping traffic for a fixed amount of time (useful outside schools) and 2) If there aren't any people crossing, the traffic should be stopped for a short amount of time no worse than if they were just a normal Pelican crossing.

However.

Even when no-one is crossing or in some case someone crossed and is about 50 metres up the road, the crossings are still usually on red for a total of often 20 seconds, which is way longer than most Pelican crossings that are on red for usually 5 to 10 seconds max.

I don't know if no-one notices or cares but it is really annoying!

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7952 4 days ago | parent [-]

My biggest annoyance are the ones that wait for a gap in the traffic. And by the time it goes green you have already crossed. They seem to be configured to be irrelevant for any able bodied person. And completely ignore current traffic conditions in favour of some hard coded delays.

	▲	hgomersall 4 days ago \| parent [-]
		Most around me seem to be in this mode. The traffic crawls past at pedestrian speed whilst a steadily growing group waiting to cross stand in vehicle fumes. There's a pretty clear principle here of flow conservation. If the light stopping traffic does not reduce overall flow then the light should change for pedestrians immediately. If the traffic flow is low, then a small reservoir is built up which clears immediately. If the flow is slow and saturated the gap that opens up can be refilled quickly. The flow range where the change actually impacts local vehicle flow is rather narrow (high, but not too high). Of course there are second order effects at associated junctions, but at that point maybe the first order interests of pedestrians should be prioritised.