In today’s headline news, the Auditor General reports that the crime rate is falling on Melbourne’s train system (e.g., see here and here). The number of incidents has remained roughly the same, while the number of commuters has gone up. So, the Transport Minister says there is more crime but the trains are safer . The Auditor General seems concerned that “Victoria Police had failed to carry out promised pilot projects designed to minimise passenger perceptions of danger on railway stations and trains”. Shouldn’t they be catching crooks instead of manipulating customer perception?
Well, if we want to play this game of statistics, here are a few additional things to consider. Many crimes probably go unreported raising questions about data reliability, but lets put that aside for a moment. The Age reports that the crime rate on Melbourne’s trains is 33 per million passengers. I did a quick web search and wow! that figure seems to be pretty high. In Boston last year there were 827 major crimes on the MBTA system out of 350 million trips, making that only 2.2 crimes per million, way below the 33 in Melbourne. Even if we only consider assaults as “serious crimes”, which TheAge reports is 17% of the incidents, that works out to 5.6 assaults per million trips. I don’t have time to find data for lots of other cities, but it appears the New York subway carries over 10 million passengers/day and sees only 5.6 crimes per day, while on the Washington Metro it is about 4.35 per million riders. Is Melbourne’s train system really that safe?
A more sensible approach is to accept that crime happens on the train/subway systems of every major city, and to try and tackle the problem. Statistics could be used constructively. For a start, explore the distribution of criminal activity. Melbourne’s trains radiate outwards from the city center and some train lines go through neighborhoods that are much more crime ridden than others. So we should be looking at the rate of criminal activity on each line separately instead of the average across the whole system. Even better, identify the location and type of criminal activity in each line segment and station, and do data mining to figure out behavioural patterns. This should inform counter measures, e.g., by putting officers on duty, adding surveillance cameras, anticipating risky situations, etc. This way, the Police might even earn the respect of commuters, instead of just hoping to manipulate their perceptions of safety.