Australia's Sydney Trains has adopted a new approach to tackling vandalism, trialling new technology designed to quickly alert staff to offenders by sniffing out spray paint vapor. While only in its infancy, the project, which know as "Mousetrap," has already produced some promising results.

Vandalism is an ongoing problem for rail companies, but it's usually difficult to catch offenders in the act. According to Sydney Trains, its workers have to remove some 11,000 tags from trains every month. In 2014, the removal of graffiti from the company's carriages racked up a bill of AUS$34 million (US$27 million) – an increase of more than 13 percent over the previous year.

To tackle the issue, the company started a new trial program, using electronic chemical sensors that detect vapor from spray paints and marker pens to catch vandals at the scene of the crime. Once detected, images captured from live CCTV cameras at the location are forwarded to Sydney Trains staff, allowing them to quickly pass those on to the Police Transport Command (PTC).

According the Sydney Trains, the trial is still in the early stages, but the results so far are very positive. The sensors have been fitted to an undisclosed number of trains, and have so far led to more than 30 arrests.

"We know it’s early days for Mousetrap but its success has been in allowing Sydney Trains to move from a strategy of removing graffiti to one where we stop it as it happens," says Sydney Trains Chief Executive Howard Collins."Our message to graffiti vandals is clear: Spray the paint and run the risk."