Is it common for pedestrian bridges to be so overbuilt? Given the weight and span it sounds like it has a cross sectional area of about 75 square feet of concrete (a little less for the steel components, but still a lot) for a mere 15 foot traffic deck. It's not crossing an especially large span nor need to carry any substantial weight other than its own, so why does it need to be so heavy?

Are they expecting trucks to run into it maybe?