Cities throughout the world spend a lot of money fighting graffiti. Graffiti writers leave their mark in public places, often on walls or other surfaces. They spray paint words, artwork or other things on buildings, trains and buses. Some graffiti writers even damage statues. Efforts by police to stop the writers often fail.
Officials in Australia have begun using a new technology that can recognize the most commonly used graffiti materials: paint and marker pens. They hope it will help police stop people from defacing walls on the passenger areas of trains.
Some passenger trains in Sydney, Australia are covered in graffiti. Surveillance cameras help police officers stop those who illegally write on train cars. But there are just too many cars in the system. Police and railroad officials cannot watch all of the cameras all the time.
Last year, Sydney Trains -- the operator of the city's rail service -- began using a new surveillance system that has an "electronic nose." Howard Collins is the head of Sydney Trains.
"We've had 50 people being charged with offenses. And as we roll it out now to other trains, it's proving even more successful."
The device is called "Mousetrap." It was developed by Technique Risk, an Australian company. 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, which is connected to a nearby surveillance camera.
"The strength of the system is the fact that security personnel or police can monitor the system in the field with a mobile phone. The information they receive is the train or carriage number, the location that the event is occurring and also where that train is going to."
Graffiti writers cannot disable the system because the sensor is hidden in the wall of the train car.
Police guard the trains and train stations. Many of the officers look like passengers. They can quickly react when Mousetrap tells them someone is painting on the walls.
Howard Collins says the system keeps a record of where and when graffiti writers are working. He says this can help officials decide where to deploy officers.
"Now we're building a profile of where or when these incidents occur. So the police already have the intelligence and the information to say ‘this is where this is likely to occur' and ‘this is the time of day.'"
Mr. Collins says Mousetrap has worked so well that most of Sydney's 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.
I'm Bob Doughty.