Study	Reason for exclusion
Beirness 2004	Review about the effectiveness of alcohol ignition interlock programs.
Gerber 2001	Prevalence study.
Jacobson 2003	Prevalence study.
Kraus 2001	Review about the effectiveness of drug testing interventions in mixed occupational settings.
Lindseth 2001	No control group.
Mumenthaler 2003	Comparison of specific psychoactive drugs on pilot performance; Intermediate measure used as outcome (flight simulator tests).
Peek‐Asa 1999	Review about the effectiveness of randomly stopping and breath testing drivers to deter from drinking and driving.
Seijts 2005	Review of perceptions toward testing.
Snowden 2007	Case ‐ control study.
Spicer 2003	Prevalence study.
Taggart 1989	Interrupted time‐series study without three measurements before the introduction of the intervention.
Wickizer 2004	Quasi‐ experimental; not specific for drug/alcohol intervention.
Zaloshnja 2006	Cost estimate study.
Zaloshnja 2007	Cost estimate study.
Zwerling 1990	Cost estimate study.
Zwerling 1992	Cost estimate study.