My friend Don, in Thailand, sends me links to articles on The Straight Dope every now and then. I got one from him today on The Metric System in the US. It's a "classic" article so it was written in 1995 and hasn't been updated. I started writing back to Don about our experience at work with the metric system, mostly after the article was written. I got a little carried away, so I decided to make it a blog entry.
Too bad Cecil hasn't followed up on that one. He mentions the 1988 law that required everything to be acquired by the federal government to be metric. This meant roads and bridges, so it affected us. At work we had to enact the switch by 1992, then it slipped to 1996. We bought new surveying equipment, upgraded our software (some of it anyway) and started designing projects in metric. It was a pain because while I have a good feeling for psi, pounds, and cubic feet, I didn't have a good feeling for Pascals, Meganewtons (we didn't use kilograms since those are masses and we wanted forces), and cubic meters. But it did make adding dimensions together really easy. Currently I have to take something like 1'-7 3/8", covert 3/8" to inches, add the inches, divide by 12 and add to the feet. I have to do this for every dimension I want to add. Then when I total them, I have to reverse process (which is why I have a program on my calculator that does this for me). With millimeters everything added up pretty easily. And I didn't have to worry about converting from cubic inches to cubic feet to cubic yards. Of course when you multiply three dimensions in millimeters, it is real easy to miss a zero when you divide by 1,000,000,000 to get it to cubic meters. The nice thing about English numbers is they were made to be relevant, but millimeters are really too small to do much with (we had a policy of dimensioning everything on bridges to millimeters) and meters are too big. Feet, inches, and yards are all in between.
Some of our programs weren't converted so we had to conceptualize bridges in millimeters, then convert all of that to feet and inches, run our old design program with these oddball feet and inches, get the results, and convert everything to metric again. So that introduced a lot of complications and room for making mistakes. The worst was probably when we had to widen a bridge that had been built in feet and come up with metric plans. So all of our dimensions were crazy metric numbers instead of the simple English numbers that were part of the original bridge. But we were dealing with it.
Then we started to actually take bids on the projects. After trying for years to get an agreement to use metric sizes, the people who supply pipe finally balked. They said they were not going to stockpile 36-inch pipe for non-government contracts along with 900 mm pipe for the government contracts. Then the rebar people said they weren't going to stock metric sizes of rebar and instead would "soft convert" rebar sizes, meaning they were going to give us the same old rebar sizes with new metric names. Instead of using 10, 15, and 20 mm bars, we had to start using the same old #4, 5, and 6 bars, but call them 13, 16, and 19 mm bars. The people who supply the lumber to build the formwork complained too and in 1998 the federal government said it would be okay to go back to English. The state governments were ignored during the design process, but once it hit the contractors it ground to a halt quickly. Alabama had changed to metric sign sizes, kilometer posts, etc. Even in Georgia, we had started using metric paper sizes! As far as I know, all of the states had made the switch to metric and now all of them have made the switch back to English. But, because we had totally switched, it took a long time before all of the old metric projects worked their way through the system (some projects take 10 years to develop), so we still have a metric project from time to time.