Back when I lived in Cambridge, someone worked out this was actually true for one of the car parks.

(Not those exact numbers, but the same point).

I lived in a city where police can fine you for biking in the night without the lights on, but police catches people so rarely that, per ride, the mathematical expectation of a fine was lower than the cost of batteries.

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throwway120385 a day ago | parent | next [-]

You really shouldn't apply statistics this way. Expected value is useful if you're an insurance company because you can price insurance products slightly above the expected value, but if the fine is $100, batteries are $90, and you get fined after going on 10 bike rides the fine doesn't magically become $10 it's still $100 and you still could've saved $10 by spending $90 before getting on your bike. That is, unless you put $10 in a piggy bank every time you get on your bicycle, and then at that point why not put $90 down and then pay yourself back $9 per ride with $1 of interest?

	▲	suslik 21 hours ago \| parent [-]
		I mean that if fine / E[N_f] < battery_cost / E[N_b], where E[N_] is an expected number of rides before a fine / battery expire, then I save money per ride. In your example, you just pick the values such that the relation becomes '>'.

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ben_w 21 hours ago | parent | prev [-]

Today? Wow. You must have very weirdly expensive batteries and/or electricity. Around here, a complete replacement of non-rechargeable bike light batteries would cost €1.25, and they'd still last more than one ride each. Rechargeable batteries may cost more, but last thousands.

	▲	suslik 20 hours ago \| parent [-]
		That was quite a while ago. I can't recall exactly anymore, but the yearly battery cost was probably indeed quite low, ~20 euro maybe? They just didn't fine people often enough.