About 23 percent of Manhattan’s 1.6 million full-time residents own cars. That’s 368,000 whips. We’re using the average workday for this little exercise; of the 1.6 million or so daily commuters, about 20 percent drive, so add 322,000 more (lots of people take the subway, but that’s underground, and we’re staying above land here). Oh, and throw in about 12,100 cabs. We’ll use 3,300 pounds as our average weight (based on the aggressively average Toyota Camry).
So 702,100 cars (and we’re probably being pretty conservative) weigh in at 2,316,930,000 pounds. That’s 1,158,465 tons. Note that we're not putting that number in bold. Because we haven’t even done buses yet. The MTA has 5,777 of those babies, each weighing around 20 tons. Let’s say they’re spread evenly across the boroughs and that Manhattan has 1,155. Toss in 100 tour buses or so. That’s 25,100 tons. For the sake of sanity, we’ll stop after adding 450 35-ton dump trucks (31,500,000 pounds/15,750 tons).
Let's not forget trains. There's 6,384 subway cars in New York and we'll assume at least half are in Manhattan. At around 38 tons each we get 121,296 tons. And actual trains? 1,200 trains pass though Penn Station daily and 700 pass through Grand Central Terminal. Your average Acela train is around 565 tons. So that's 1,073,500 tons.
Add it all together and you get a conservative number of 2,394,111 tons. Whoa.