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From VOA Learning English, this is the Technology Report. Words or pictures put on public property without permission is called Graffiti. Graffiti writers paint or draw on buildings, trains and buses. Often, they use spray paint from a can. Some graffiti writers even damage statues. Efforts by police to stop them often fail.
Officials in Australia are using a new technology that recognizes paint and marker pens. Some passenger trains in Sydney are covered in graffiti. Cameras help police officers stop those who illegally write on train cars. But police cannot watch all the cameras. Sydney Trains operates the city’s rail service. Last year it began using a new system with an “electronic nose.” The device is called “Mousetrap.” Developed by the company Technique Risk, Mousetrap can identify gases released by markers and spray paints. Mark Byers founded the company. He says when the device recognizes the smell of graffiti, it sends a message to an alarm and camera. It tells officials the train number, the location of the act, and where the train is going. The sensor is hidden in the train’s wall, so writers cannot disable it. Police guard the trains and train stations, sometimes looking like regular people. They can quickly react when Mousetrap tells them someone is painting on the walls. Howard Collins heads Sydney Trains. He says Mousetrap has worked so well that most trains are now free of graffiti. He says it cost about $500,000 to put the system in place. But he says that is not a lot of money compared to the $34 million Sydney Trains spent last year to remove graffiti.