Table 3 Prevalence of taking drugs by time at which specimens were provided among drivers under and over the limits for alcohol.

Time specimen provided	Drivers under limit, number positive/number of samples; % (95% CI)	Drivers over limit, number positive/number of samples; % (95% CI)
6 am–4 pm	48/94; 52.1 (41.6 to 62.4)	10/47; 21.3 (11.2 to 36.1)
4 pm–9 pm	47/115; 40.9% (31.9 to 50.4)	18/111; 16.2 (10.1 to 24.7)
9 pm–6 am	236/791; 29.8 (26.7 to 33.2%)	114/842; 13.5 (11.3 to 16.1)