Re: Silverton Line Question--Economics

It's not so much a change in technology as it is a change in the relative cost of materials versus labor. Taking a look at the lattice girders, it is easy to see lots of labor there with all of the individual parts, all the holes to drill, and all the rivets to install. Plus the capacity of the bridges is probably less than the new one. So less material and more labor when labor was cheap. Much more material in the heavy steel sections of the new bridge but it is probably stronger and required less labor in assembly. The material probably cost more because of price inflation but less labor was required which was more costly.