Innumerate reporters calling a 7/1 against event a miracle
Posted Fri, 2007-05-04 06:22
The news from Toronto this morning was of a chunk of concrete falling from an old overpass onto the Gardiner Expressway during heavy 7am traffic. The Gardiner is the main - and only - radial expressway into downtown Toronto from the west. It's old. Here's how one report described it:
"Call it a morning miracle.
"A huge chunk of concrete about the size of a loaf of bread fell from the Kipling Bridge onto the busy Gardiner Expressway around 7am Thursday.
"And despite the fact the highway was jammed with cars, it somehow missed every one of them, landing harmlessly on the side of the road." (CTV Toronto City News CP24)
Now calling it a miracle that the concrete chunk didn't hit a car implies the odds are strongly that anything that falls on a busy roadway will hit a car when traffic is heavy. On the contrary the odds are at least seven to one AGAINST a single random fall of a concrete chunk, or any other dropping object, hitting a car in heavy traffic.
Here's the calculation:
In dense stop and go traffic say Level of Service F vehicles are spaced on average about 80 to the mile - http://people.hofstra.edu/geotrans/eng/ch6en/meth6en/highwaysfd.html
80 cars to the mile/lane is an average 66ft front bumper to front bumper. That means the envelop area within which each vehicle is traveling is 66ft by the width of the lane say 12ft or 792 sq ft. With an average car measuring 18ft x 6ft the 'target area' of the average car makes up 108 sq ft. That means that even in dense traffic the chances are just over seven to one AGAINST (792/108) a single lump of concrete falling and hitting a car.
Or the probability is such that you should expect for every 7 lumps of concrete that fall one car would get hit on average.
Now of course a 1 in 7 chance of getting hit isn't good either and they need to fix the 50 and 60 year old bridges, but reporters disgrace their profession when they show themselves lacking the most elementary grasp of probability with idiotic exclamations of the expected as miraculous.
TOLLROADSnews 2007-05-03
"Call it a morning miracle.
"A huge chunk of concrete about the size of a loaf of bread fell from the Kipling Bridge onto the busy Gardiner Expressway around 7am Thursday.
"And despite the fact the highway was jammed with cars, it somehow missed every one of them, landing harmlessly on the side of the road." (CTV Toronto City News CP24)
Now calling it a miracle that the concrete chunk didn't hit a car implies the odds are strongly that anything that falls on a busy roadway will hit a car when traffic is heavy. On the contrary the odds are at least seven to one AGAINST a single random fall of a concrete chunk, or any other dropping object, hitting a car in heavy traffic.
Here's the calculation:
In dense stop and go traffic say Level of Service F vehicles are spaced on average about 80 to the mile - http://people.hofstra.edu/geotrans/eng/ch6en/meth6en/highwaysfd.html80 cars to the mile/lane is an average 66ft front bumper to front bumper. That means the envelop area within which each vehicle is traveling is 66ft by the width of the lane say 12ft or 792 sq ft. With an average car measuring 18ft x 6ft the 'target area' of the average car makes up 108 sq ft. That means that even in dense traffic the chances are just over seven to one AGAINST (792/108) a single lump of concrete falling and hitting a car.
Or the probability is such that you should expect for every 7 lumps of concrete that fall one car would get hit on average.
Now of course a 1 in 7 chance of getting hit isn't good either and they need to fix the 50 and 60 year old bridges, but reporters disgrace their profession when they show themselves lacking the most elementary grasp of probability with idiotic exclamations of the expected as miraculous.
TOLLROADSnews 2007-05-03