It's easier if you look at (say) Australian road traffic enforcement statistics; they have different rules than the US, have the "right" to check for DUI without having to make up a reason, and operate by funnelled road blocks that check everybody (or every second car, etc, depending on flow rates and breath check speeds).
They also 'verify' in the sense that any driver can challenge and get a "better than road side" test back at the station under supervision (blood tests with saved samples for court challenges, etc).
