Take a close look at these pictures of a San Francisco cable car.
Can you tell what's wrong with it?
Answer: It's not a cable car!
No, it's not a cable car. It's an electric streetcar. What's the difference? A quick refresher: San Francisco's classic cable cars are unpowered vehicles propelled by grabbing on to a moving underground cable with a giant metal clamp, or grip. Mechanically, it's no exaggeration to say that a cable car is far more closely related to, say, a ski lift, than a contemporary bus or tram.
But if you look at the car shown here, you'll notice a thin black arm that extends up from the roof. That's the big clue. It's a trolley pole, which is used to transfer electricity from overhead wires to the electric motors that give this streetcar its mojo.
San Francisco Streetcar No. 578 was built in in 1895, and according to the folks at Market Street Railway, it may be the world's oldest streetcar still on the active roster of an urban transit agency. It still runs for special events, and it looks almost good as new, although No. 578 does contain some nifty cues that hint at its true age:
But what explains No. 578's uncanny resemblance to a cable car?
That answer is pretty simple. 578 looks like a cable car because when it was built, this is what all public transit vehicles had looked like since the basic infrastructure of modern public transportation was invented in the 1830s. Indeed, the appearance of No. 578 -- and the cable cars, for that matter -- is derived from the shape of the first true mass transit vehicle, the horse car, or horse-drawn streetcar. Here's a horse car from 1877:
Cable cars came along in 1873, and cable car vehicles were basically built to look like horse cars -- only with the horse lopped off. Then things got really exciting. Thomas Edison patented his system for electric power distribution in 1880. Urban electrification followed, as did the development of the electric streetcar, in 1888.
Electric streetcars simply embraced the conventional design vocabulary of the times, which explains why streetcar No. 578 looks like a cable car which looks like a horse car.
So there you have it.
Images: Telstar Logistics