New York City's Domain Awareness System has 6,000 video surveillance cameras linked together, there are over 4,000 cameras on the subway system although nearly half of them do not work, and two thirds of large apartment and commercial buildings use video surveillance cameras. In the Washington D. C. area, there are more than 30,000 surveillance cameras in schools, and the Metro has nearly 6,000 cameras in use across the system. The Cheshire figure is regarded as more dependable than a previous study by Michael McCahill and Clive Norris of UrbanEye published in 2002. Based on a small sample in Putney High Street, McCahill and Norris extrapolated the number of surveillance cameras in Greater London to be around 500,000 and the total number of cameras in the UK to be around 4,200,000. According to their estimate the UK has one camera for every 14 people. Although it has been acknowledged for several years that the methodology behind this figure is flawed, it has been widely quoted. Furthermore, the figure of 500,000 for Greater London is often confused with the figure for the police and local government operated cameras in the City of London, which was about 650 in 2011. Project SCRAM is a policing effort by the Halton Regional Police Service to register and help consumers understand the complex issues of privacy and safety that confront households when dealing with installations of home security systems. "The SCRAM program enables community members to voluntarily identify and register their residential video surveillance equipment through a simple, secure, confidential, online form.