Purpose: This study first aimed to investigate the differences in drug driver detection rates between a trial of randomised and targeted enforcement operations. The second aim was to identify which indicator categories are most commonly used by police to target drug drivers and to assess the effectiveness of targeted drug testing. Finally, this study aimed to quantify what specific indicators and cues (of the overarching categories) triggered their decision to drug test drivers and which indicators were most successful.

Design/methodology/approach: This research examined the detection rates in a trial comparison of randomised and targeted roadside drug testing (RDT) operations as well as the methods utilised by police in the targeted operations to identify potential drug driving offenders.

Findings: Visual appearance was by far the most commonly utilised indicator followed by age, police intelligence on prior charges, vehicle appearance and behavioural cues. However, the use of police intelligence was identified as the most successful indicator that correlated with positive oral fluid testing results. During the randomised RDT operations, 3.4% of all drivers who were tested yielded a positive roadside oral fluid result compared to 25.5% during targeted RDT operations.

Research limitations/implications: The targeted RDT approach, while determined to be an effective detection methodology, limits the overall deterrent effect of roadside testing in a more general driving population, and the need for a balanced approach to ensure detection and deterrence is required. This study highlights that by focussing on night times for randomised RDT operations and the identified effective indicators for targeted operations, an effective balance of deterrence and detection could be achieved.

Practical implications: While the presence of a single indicator is not indicative of a drug driver, this study highlights for police which indicators currently used are more effective at detecting a drug driver. As a result, police could adapt current RDT procedures to focus on the presence of these indicators to support drug driver detection.

Originality/value: This is a world-first study that examines both randomised and targeted roadside drug testing. This study controls for location and time of day while using the same police unit for roadside testing, thus is able to make direct comparisons between the two methodologies to determine the effectiveness of police targeting for roadside drug testing. Furthermore, this study highlights which indicators used by police results in the highest rate of positive roadside drug tests.