When a photo of a heavily graffiti tagged Toronto subway train was posted to Reddit on Sunday, it came as something of a surprise to the TTC. Since David Gunn's tenure as general manager in the late 1990s, the transit provider has had a strict policy of keeping heavily vandalized trains out of sight.

"It's a bit of the broken window theory," says TTC spokesman Brad Ross. "We will take trains out of service, or buses, or streetcars if it has been significantly vandalized, and the reason for that is we don't want it to become viral."

When Gunn took over as president of the New York City Transit Authority in 1984, graffiti was so widespread that some trains were coated inside and out with tags. Management had spent decades and countless dollars cleaning and periodically repainting trains.

As part of Gunn's wider rehabilitation of the New York subway, he instituted a policy of pulling tagged trains from service, even during rush hour, a concept he brought to Toronto in 1995. The theory goes that if damage and graffiti become normal for riders, it could lead to more severe acts of vandalism.

Gunn's policy hasn't eliminated graffiti on the Toronto subway, however.

"Last year we had around 70 reports. That's everything: inside trains, on vehicles, stations, all TTC property," says Brad Ross. "We don't include 'scratchiti' in that, but [it's] Sharpies and spray paint or whatever marker."

As you might expect, tagging a subway train is risky business. The third rail, the source of the high-voltage electricity used by trains, is always live and tunnels are in constant use, even after the end of scheduled service. People die trying to paint trains.

In the case of last weekend's tagged train, Ross says the incident likely occurred as a result of track work between Bloor and Eglinton stations. Instead of being kept in a fenced and closely watched yard overnight Saturday, the train was stored on the tracks somewhere near Finch station.

Staff didn't notice the damage and the train was allowed to enter service, Ross says. It was pulled and an investigation launched soon after. It took several hours to clean with solvents, but the train is now back in use on Line 1.

"People shouldn't have to look at vandalized vehicles for which they own and pay for, and so we have an obligation to ensure they are kept clean and presentable for the people of Toronto."

Photo by Peter Muzyka

Chris Bateman is a staff writer at blogTO. Follow him on Twitter at @chrisbateman.