Sometime, somewhere along the line, somebody had one of those light-bulb moments and realized that hundreds of big things the size of a highway billboard were rolling the streets of Chicago around-the-clock, every day.
And some genius surely said to himself: "What if they actually were covered with billboards?"
Those rolling ads were, of course, Chicago Transit Authority buses, and the rest, as they say, was history.
But how do you wrap an ad the size of a bus, on something as big as ... a bus?
"It's just pressure sensitive adhesive vinyl," says Brian Zemlanicky of Titan Worldwide, the advertising contractor which buys space on the CTA. "Each bus has its own template so that the design matches the exterior of the specific bus."
It may look like a big shrink-wrap, which would, of course, require a really big hair dryer to finish the job. Actually, the process is much more like wallpaper. The ads are printed on 22 giant sheets of vinyl, ten on each side of the bus, with two in the back.
"We don't wrap anything on the front of the bus, so that passengers or commuters can see that it's actually a CTA bus, and not some other bus."
Once each strip is stuck to the bus, the entire ad is trimmed around window and door frames, lights and other critical areas. Then the ads are cut from the windows and identical panels printed on perforated vinyl are applied. Those look just like the original ad on the outside, but they allow riders to look through the windows from inside the bus.
"We're only allowed to install ads on 50 percent of the windows," Zemlanicky explains. "The vinyl that's placed on the windows has very small holes. Fifty percent of the material is advertisement, 50 percent is holes."
At any given time, 100 to 150 buses carry at least partial wraps on the CTA. And its a lucrative proposition for the transit agency.
Under the 2010 contract, the CTA is guaranteed a minimum of $14 million.