Vizcaya transporter bridge: Getting there is half the fun
What do you do when you have to build a bridge, but you don't have a lot of room for all those ramps, and you still have to let shipping get through? Draw bridges and swing bridges are one way, but they are very expensive, having to lift entire roads.
In 1893 a disciple of Gustave Eiffel, Alberto Palacio, figured out another way: The transporter bridge. The Vizcaya Bridge in Bilbao, Spain is a suspension bridge built about 150 feet above the water, with a 36 wheeled cart that is pulled across. Hanging from it on 70 cables is a gondola that can carry freight and people; four million people and half a million cars use it every year.
When the gondola is out of the way, it can permit the passage of serious ships. Yet it take up very little space on either shore.
They sort of have defeated the purpose of the whole thing by building an elevator at either end so that people can walk across the top, but it is still an interesting bit of engineering. They should put one across Toronto's Eastern Gap to the islands so that people don't have to wait half the day for the overcrowded ferries.
The Middlesbrough Transporter BridgeAnne on Flickr/CC BY 2.0
There are a few of these in Britain, but they do not appear to have been built in such urban settings. Still, you can see the economy of it all, a light structure with its ends restrained by cables to minimize the steel needed. The Middlesbrough bridge is still in use;
Middlesborough Bridge opening/Public Domain
While these bridges can and do carry cars, they were designed in a time when the car didn't dominate all the infrastructure. So you could get people, bikes and a few work vehicles across the water in a lot less space, with a lot less steel, at a lot less cost. Looks like fun, too.