MTO Contrast Compliance Checker
Ontario Regulation 424/97 requires commercial vehicle lettering to be in “high contrast” to the vehicle body — but the regulation never defines a specific ratio. We use the internationally accepted WCAG 2.1 relative luminance algorithm to mathematically verify your colour combination before you order.
🔬 MTO Contrast Compliance Checker
O. Reg. 424/97 requires “high contrast” lettering. We use WCAG 2.1 math to verify compliance before you order.
Optimal — visible at highway speed
WCAG 2.1 minimum: 4.5:1 • Highway visibility recommended: 7.0:1
Based on W3C WCAG 2.1 relative luminance algorithm adapted for vehicle signage. Not legal advice — verify with your compliance officer.
How It Works
The Math
For each colour, we calculate its relative luminance using the sRGB colour space formula from WCAG 2.1. The contrast ratio is then:(L1 + 0.05) / (L2 + 0.05)where L1 is the lighter colour. A ratio of 1:1 means identical colours; 21:1 is the maximum (black on white).
What the Thresholds Mean
| Ratio | Verdict | Meaning |
|---|---|---|
| 7.0:1 + | Optimal | Visible at highway speed, any weather. Exceeds all standards. |
| 4.5:1 – 6.9:1 | Pass | Meets minimum contrast. Consider adding a contrasting outline for visibility. |
| Below 4.5:1 | Fail | MTO officer may deem non-compliant. We block this combination to protect you. |
Why This Matters
Every year, thousands of Ontario carriers receive fines at weigh stations for non-compliant door lettering. The most common issue? Choosing a vinyl colour that looks fine in a garage but is unreadable at 100 km/h on the 401. Our compliance checker eliminates that risk entirely — if the math says fail, we will not print it.
⚠️ Legal Note: O. Reg. 424/97 uses the term “high contrast” without defining a numeric threshold. The 4.5:1 ratio is our engineering standard based on WCAG accessibility science. When in doubt, use white lettering on a dark vehicle or black lettering on a light vehicle.