Comment by ndsipa_pomu

One point is that traffic lights are designed for the benefit of drivers. Most of the time, cyclists can easily and safely navigate through a red light as they take up so much less space than cars. e.g. turning left at a junction (assuming UK driving on the left) can be done without causing any inconvenience for drivers and will often be safer for a cyclist than having to wait at a red light and then deal with drivers who've only just looked up from their phone and might not have seen you.

It's notable how RLJing differs between cyclists and drivers. RLJing drivers will see a light turn to amber and then speed up so that they can get through the junction before the other directions can start moving. Obviously, speeding up to RLJ is very dangerous to pedestrians who might be crossing.