Warn Range
The "warn range" in Ontario refers to a blood alcohol concentration between 50 and 99 milligrams of alcohol per 100 millilitres of blood — below the criminal threshold of 80 mg but above the threshold for administrative penalties under the Ontario Highway Traffic Act. The warn range exists because impaired driving research shows meaningful impairment at BACs lower than the criminal threshold; the administrative penalties bridge the gap.
Mass Tsang focuses on criminal defence, but the firm regularly advises clients on warn range implications that arise alongside criminal driving files. For more on roadside screening, see our blog post on how police use roadside screening tools in Ontario.
How warn range is detected
Warn range readings are produced by roadside Approved Screening Devices (ASDs). The ASD provides one of three readings: PASS (below 50 mg), WARN (50–99 mg), or FAIL (100 mg or higher). A WARN reading does not provide grounds for a criminal charge but triggers immediate administrative consequences under sections 48 to 48.3 of the HTA. Mandatory alcohol screening since 2018 means any lawfully stopped driver can be required to provide a roadside sample.
Penalties
Warn range penalties escalate with repeat occurrences within five years: first occurrence — immediate roadside licence suspension of 3 days, $250 administrative penalty; second occurrence — 7-day suspension, mandatory alcohol education program (Back on Track), $350 penalty; third or subsequent occurrence — 30-day suspension, mandatory alcohol treatment program, $450 penalty, mandatory ignition interlock for 6 months.
Insurance consequences
Insurance impact is significant. Warn range incidents are reported to the Ministry of Transportation and become part of the driver's record. Insurance companies treat warn range incidents as classified offences and apply substantial premium increases. The increases can last 3–6 years. For drivers in certain occupations or those holding professional licences requiring vehicle access, the consequences can extend further.
Warn range is not a criminal charge
Importantly, a warn range incident does not create a criminal record. It is administrative — not a Criminal Code conviction. The driver retains the right to remain silent (though there is no point doing so in the administrative context). There is no court process, no trial, and no Charter scrutiny of the same kind that applies to criminal proceedings. The administrative review process is limited and rarely results in reversal.
Practical implications
The existence of the warn range means there is no "safe" amount of alcohol before driving in Ontario. Even one or two drinks can produce a warn-range reading depending on body weight, food intake, and timing. The penalties are real, the insurance impact is significant, and the warn range stays on the driver's record. For repeat warn-range incidents, the consequences approach those of a criminal conviction.
Related glossary terms
