Actually they do. The temp lights MUST allow time for a vehicle to travel through while the lights are on an "all red" phase. This is to allow for cars trucks etc "nipping in" and to clear the way for oncoming traffic. If the lights do not allow enough time you have the right to request that the timing be altered, [the traffic management operatives are not fools however and will spot someone taking the p--s, so don't pretend you can only manage 2 mph].
The sensors do see cyclists the problem is many people slide up to them at 2 - 3 mph and wait, many sensors operate at approach speeds of over 5mph [to allow for non actuation by pedestrians] and it's best to try to approach "head on" as your apparent speed will be less visible at an ange to the detector head.
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Sadly that has not been my experience, espescially at longer sets of roadworks where we usually just end up back the other side of the cones if we meet oncoming traffic, waiting for the next phase and rarely if ever have we been able to talk to the workmen - usually (when we cycle/time of day) they are not around or if they are invariably seem to be at the other end of the road works from where the issues occur, or they just nod hello and ignore the issue.
However, before you write me off as one of "those", you will find that in
this thread, I am actually defending the state of the UK roads. I know that people don't appreciate the condition they are - i.e. usually very good/excellent for most of the time. They are significantly better than many other countries I have cycled in, including some very close to home and last year we covered 22 countries and that does take a lot of work and effort, so thank you. Some of us, do really appreciate you.