Wow! I just watched a tractor trailer make a u-turn where most people have trouble in a normal car. I was thinking that this would make a great blog entry but when I started to dig into the technical details it started to get pretty muddy.
First off, I needed to figure out how wide the road was. Short of getting out and measuring it, I turned to the Internet. The road was a 4-lane road with a concrete curb median (so, 2 lanes in each direction). The State of Maryland lists the standard lane width for a state road under 40 mph as 11 feet (with an absolute minimum of 10 feet). Now, the road I was on was a ring road around Frederick Mall, probably not a state maintained road, but it gets me close. No fire lanes, so from curb to curb 44 feet at best.
Back to the Internet. TruckersReport.com has diagrams for a standard truck (69 feet long) and how wide the road should be to achieve a certain radius turn. According to this website, the minimum road width requirement for a 180 degree turn is 33 feet.
Given all of this information, the truck had 11 feet to spare taking into account all four lanes, but he needed to avoid the concrete curb in the median - something that he managed to accomplish.
Do you think all of this went through his head before he made the u-turn? I don't think so. I suspect he accidentally turned down this mall road and realized that he didn't want to be there. He took the first opportunity to turn around - happened to be in the middle of an intersection - and pulled it off like a pro. I suspect he just got lucky.
The 180 degree turn radius below is the one that I am interested in.
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