Attacks on meter maids in London are now so common that parking control officers are being given DNA swab kits to identify anyone who spits at them. A private lab matches the DNA samples against a national police computer database to identify any matches for prosecution on a charge of common assault, which carries a maximum sentence of 6 months in prison. Parking tickets generated over £1 billion (US $1.8 billion) in revenue last year.

NCP security chief Gordon McLardy said: "Spit kits have already been used by Transport for London and a number of bus companies and have led to a marked reduction in incidents."