On my friend's way home from work is a notoriously busy intersection at which the lights take up to three minutes to change, and long queues of cars quickly build up. He arrived at the lights at the front of the queue, just behind a lady on a motor scooter. After a while, the lady comically put her hand to her head, felt around and realised she'd forgotten her helmet. She slapped her face with her hands, put the scooter on its stand, walked to the pannier and retrieved the helmet. Naturally she did this while the lights were green, and blocked any cars from getting through. Everyone patiently waited for the lights to change again but they never did - it cycled through the pattern six or seven times, skipping their turn. Being scientifically minded, my friend realised that because the vehicles in his queue were stationary, they were not generating any electric current in the magnetic loop buried under the road. So the lights were not detecting the presence of the ever-growing lines of grumpy drivers. He solved the problem by gradually edging forward over the magnetic loop, and finally the lights responded.
Let that be a lesson to you, should you ever be in such a situation.
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