What happens is someone has a B/A content of say, for example: .001 and has a G2 license. Small amounts don't necessarily impair an individual. What is the penalty? Is it just as bad as having an .08 with a G?
G2 driver with .001 would be charged under the HTA with Class G2 Licence Holder -drive when blood alcohol concentration above zero ( Sec 6(1) Reg 340 HTA).
As well, the concentration of alcohol does determine impairedness. For example, a seasoned drinker can blow 200 and have very little signs of impairment verses a non-drinker, who could blow 65 and be severely impaired.
It is common for DRP to charge people that blow under the legal limit .08 with impaired if the driving evidence and symptoms of impairment can corroborate the charge.