BACKGROUND: This study aimed to assess the early impact of national alcohol trading hour restrictions on night-time violence in New Zealand. The new national maximum trading hour restrictions prohibited 24-hour trading by reducing hours to between 8am and 4am for on-premises and between 7am and 11pm for take-away outlets.
METHODS: A telephone survey of alcohol outlets was undertaken to determine actual trading hours before the law change. Interrupted time-series analysis modelled weekly night-time police calls for service for assault (i.e. between 9pm-6am) and late-night police calls for service for assault (i.e. between 4am-6am) from 2005 to 2015. Day-time police calls for service for assaults were used as the comparison group. Abrupt permanent changes and gradual permanent changes were assessed.
RESULTS: The survey found that only 1% of alcohol shops, 9% of supermarkets and 6% of bars/nightclubs were affected by the hour restrictions because they did not trade as long as their licensed hours permitted in the first place. The time series analysis found no effect of the national trading hour restrictions on night-time police calls for service for assaults. However, a significant gradual permanent decrease of 12.4% was found for late-night assaults between 4am and 6am (i.e. those likely related to the on-premises hour restriction). This equated to a weekly average decrease of 4.3 police calls for service for assaults between 4am and 6am following the law change.
CONCLUSIONS: The national trading hour restrictions for on-premises and take-away outlets affected only a small proportion of premises and accordingly the restrictions had no impact on the overall level of night-time violence. Late-night assaults likely related to on-premises, however, did reduce showing the effectiveness of trading hour restrictions even when the impact of the law change on the ground was minimal.