The law does not prescribe maximum permissible levels for noise from motor vehicles and the police do not therefore need noise level meters for law enforcement purposes. In 1963 there were 2,960 prosecutions in the Metropolitan Police District for offences relating to vehicle noise, of which 2,913 were successful; 489 cautions were also issued. There were 16 prosecutions for sounding horns when stationary or in the proscribed hours, all of which were successful; 30 cautions were also issued for such offences.