Also from the article:

>There's a city-specific reason why San Francisco has stuck with wood rather than swap over to metals, and the answer lies in looking up. The high-voltage cables and wires that guide the city's (oft-maligned) public transport system Muni, and trolley cars crisscross above nearly every street, mean that ladders made of conductive elements are generally just too dangerous to use.

>"I think there's a lot of fire departments that went aluminum and wish they could go back to wood but it's too expensive," Braun says. "There's only two ladders manufacturers in the states—and we're one of 'em. We only make our own ladders and can barely even keep up with what we have."