There is an increasing number of car accidents in New Zealand associated with drug driving. This led to the creation of the Land Transport (Drug Driving) Amendment Bill 2020, which will, if enacted, implement per se drug driving laws and an RDT (random roadside drug testing) scheme; this will include driving regulations of impairing prescription medication. In this study, impairing therapeutic concentrations of benzodiazepines (a large category of newly regulated medication) were determined using a meta-analysis of controlled studies on the impairment resulting from doses/dosages of benzodiazepines. Along with datasets of impaired drivers’ blood concentrations, which were used to verify impairing blood-drug concentrations found in the meta-analysis. It was found that some therapeutic doses/dosages of benzodiazepines resulted in impairment more than others, such as diazepam and lorazepam, which are used multiple times daily to maintain a therapeutic blood concentration. These results were then used to critique the blood-drug concentration statutory and threshold limits proposed by Poulsen et al. (2021). It was concluded that limits set for diazepam did not reflect impairing concentrations. Labelling of pharmaceuticals and the propensity of physicians and pharmacists to warn patients about impairing medications was investigated by analysing CALs (cautionary advisory labels) and the pharmacists code of ethics. It was concluded that there needs to be more effort into informing patients and the public of the risks of drug driving.