Today marks the beginning of road side drug testing - starting exclusively in the Wellington District.

The scheme's pilot will see police conducting random roadside saliva tests - screening for cannabis, methamphetamine, MDMA, and cocaine.

The initiative begins in the capital before scaling up from April until coverage is nationwide by mid next-year.

Any drivers whose tests come back positive, will need to do a lab test which also checks for 25 other substances.

Positive tests can result in 12 hour disqualifications from driving and possible infringement notices.

Police Association President Steve Watt shares his thoughts.