The bag of cat treats had an oddly specific recommendation: a cat could have up to 17 per day. Why exactly 17, I wondered.
In high school I was taught the difference between accuracy and precision. I would have had a red mark on my test if I made such a recommendation. Cats vary a lot in weight and activity. Round the number off to 10 or 20.
Before a number goes up on a traffic sign, the people who put it there should understand why it should not be lower or higher. That’s two questions, and they need to be able to answer both.
At a city traffic council meeting I heard an explanation why parking time limits should be one or two hours. A shorter time limit didn’t let visitors do their business. A longer time limit was hard to enforce because a police officer had to visit the same block twice during a four hour shift to write a parking ticket. The reason is a limitation of one city’s enforcement technology, but at least it’s a reason.
Or no parking 7-9 AM. The goal was not to free a lane during rush hour. The goal was to keep nonresidents from parking in the neighborhood without requiring residents to get permits. Most nonresident parking is by people who need to be at work by 9 AM. That explains the end time. The no parking period has to be long enough for a police officer to find time to drive past. That explains the start time. It may not be a good policy — I want to ban xenophobic parking laws — but as a means of implementing an enforceable policy the rule makes sense.
Yellow light duration — the time you get to decide whether to stop at a light — can also be explained. As the signal gets longer compliance goes up, but once compliance is over 95% there isn’t much point in going longer. There will always be a small rate of violations no matter how long the yellow is and no matter how well the red is enforced. With 95%-99% compliance everybody approaching when the light turns yellow is able to stop in time and cross traffic doesn’t have to wait unnecessarily. (Notice I’m not quoting a formula and I’m not saying any particular light is timed properly. They could be timed properly, to accomodate the humans who rely on them.)
The usual excuses for posting low speed limits fail this test.
A common explanation goes like, “the faster you go the harder you hit”. So what? All that says is driving should be forbidden, because you could always drive slower and supposedly safer. In fact we routinely drive at speeds that come with a 400% chance of death, according to one of the standard measures, because most of us are not ramming concrete pillars head-on. And we aren’t usually ramming pedestrians head-on at cruising speed, as I explained when Boston proposed a lower speed limit.
A Melrose City Councilor said she felt relaxed driving at 25. So what? Do other people feel relaxed? Would she feel more relaxed at 20? I’m betting most of her driving constituents feel more relaxed at 30-35 and won’t make the connection between her ignorance and their tickets.
Another explanation I’ve heard is “people aren’t ready for…” At least there’s a little honesty. If somebody says a speed limit reduction is a prelude to another speed limit reduction, believe that and oppose the first one.
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