Truck traffic on Ambassador Bridge greatly exaggerated - like by 35% to 40%
Again and again you'll read that the Ambassador Bridge handles 10,000 trucks per day. The Detroit-Windsor media report the "ten thousand daily" almost, well, daily. Wikipedia has it too.
The bridge company itself is partly at fault. They say on their website the bridge "carries more than 10,000 commercial vehicles on a typical weekday."
The word typical introduces the sense of most common but we won't try getting into averages that capture that with medians and modes. (It's too long since we did college Statistical Method!)
But weekdays are higher than average days if few drive on weekends, so it is possible they get near 10,000 on average weekdays, but on the official data of the Public Border Operators Association, it's most unlikely.
By end June this year 1,351,825 trucks had traveled the Ambassador Bridge or an average of 7,407 per day (1,351,825/182.5.) If no trucks travel weekend days - zero trucks on Saturdays and Sundays - then the average weekday gets 1,351,825/132.3 or 10,217.
The simplest way to figure average daily truck traffic is the reported total number for 2011: 2,614,988/365 = 7,164.
Media's sloppy ten grand number
10,000/7164 = 1.396
10,000/7407 = 1.35 (CORRECTION)
"Ten thousand a day" is therefore a 35% to 40% exaggeration.
There was a time when the Ambassador Bridge did 10,000 trucks a day average. But you have to go back a ways to get even close. 2006 they did 3,498,127 trucks, an average daily 9,581.
The days of 10,000 trucks a day average Detroit-Windsor are long since gone, even if the news hasn't got to the newsrooms there.
CORRECTION JULY 19 08:45