Dear Rabbi Simon
Sensors were recently installed outside our block of flats which automatically come on when someone enters or leaves the block. Sometimes, we need to go out in the evening on Shabbat or yom tov (e.g. going to hosts for a meal). What implications does this have for Shabbat and Yom Tov observance?
Many thanks,
Esti
Dear Esti
The situation you describe is unfortunate, in which the sensors have been introduced to your surroundings, presumably without your having the opportunity/authority to endorse or reject the proposal.
Under the circumstances, I would permit you to come and go as usual. You should try to minimise any benefit that you may inadvertently derive from having activated the lights (through the sensors). An example of the benefit to avoid would be utilising the illumination for the purpose of reading.
I hope this is helpful.
Best wishes
Rabbi Rashi Simon