Background: Workforce alcohol and drug testing is commonplace but its effect in reducing occupational injuries remains unclear.

Objectives: To assess the effects of alcohol and drug screening of occupational drivers (operating a motorised vehicle) in preventing injury or work-related effects such as sickness absence related to injury.

Search strategy: We searched the following databases up to June 2007 (or up to the latest issue then available): MEDLINE, EMBASE, The Cochrane Library, Cochrane Occupational Health Field's specialised register, DARE, PsychINFO, ERIC, ETOH, CISDOC, NIOSHTIC, TRANSPORT, Zetoc, Science Citation Index and Social Science Citation index and HSELINE. We also searched reference lists, relevant websites and conducted hand searching.

Selection criteria: Randomised controlled trials (RCTs), cluster-randomised trials, controlled clinical trials, controlled before and after studies (more than three time points to be measured before and after the study) and interrupted time-series (ITS) studies that evaluated alcohol or drug screening interventions for occupational drivers (compared to another intervention or no intervention) with an outcome measured as a reduction in injury or a proxy measure thereof.

Data collection and analysis: Two review authors independently extracted data and assessed study quality. We contacted authors of the included studies for further information.

Main results: We included two interrupted time-series studies conducted in the USA. One study was conducted in five large US transportation companies (N = 115,019) that carried passengers and/or cargo. Monthly injury rates were available from 1983 to 1999. In the study company, two interventions of interest were evaluated: mandatory random drug testing and mandatory random and for-cause alcohol testing programmes. The third study focused only on mandatory random drug testing and was conducted on federal injury data that covered all truck drivers of interstate carriers.
We recalculated the results from raw data provided by the study authors. Following reanalysis, we found that in one study mandatory random and for-cause alcohol testing was associated with a significant decrease in the level of injuries immediately following the intervention (-1.25 injuries/100 person years, 95% CI -2.29 to -0.21) but did not significantly affect the existing long-term downward trend (-0.28 injuries/100 person years/year, 95% CI -0.78 to 0.21).

Mandatory random drug testing was significantly associated with an immediate change in injury level following the intervention (1.26 injuries/100 person years, 95% CI 0.36 to 2.16) in one study, and in the second study there was no significant effect (-1.36/injuries/100 person years, 95% CI -1.69 to 0.41). In the long term, random drug testing was associated with a significant increase in the downward trend (-0.19 injuries/100 person years/year, 95% CI -0.30 to -0.07) in one study, the other study was also associated with a significant improvement in the long-term downward trend (-0.83 fatal accidents/100 million vehicle miles/year, 95% CI -1.08 to -0.58).

Authors' conclusions: There is insufficient evidence to advise for or against the use of drug and alcohol testing of occupational drivers for preventing injuries as a sole, effective, long-term solution in the context of workplace culture, peer interaction and other local factors. Cluster-randomised trials are needed to better address the effects of interventions for injury prevention in this occupational setting.