Maximum Height Clearance Sign

Introduction

This warning sign alerts drivers—especially those operating tall vehicles like trucks, RVs, or buses—of height restrictions on the road ahead. The height shown (in this case, 3.9 meters) indicates the maximum vehicle height that can safely pass. Recognizing and responding to this sign is essential for avoiding serious accidents and is part of the Ontario G1 driving test knowledge base.

What Does This Sign Mean?

This sign includes:

• A yellow diamond-shaped background (indicating a warning)

• Two arrows, one pointing up and one down, with a number in between (e.g., 3.9 m)

It means:

• The space between the road surface and the overhead structure (bridge, tunnel, overpass) is 3.9 meters

• Vehicles taller than 3.9 meters must not proceed

Where Is This Sign Typically Placed?

• Ahead of low bridges or overpasses

• At tunnels or parking garages

• Near underpasses and loading bays

• Sometimes on detour routes for large vehicles

How Should Drivers Respond?

• Check your vehicle height before approaching

• If your vehicle exceeds the posted height, take an alternate route

• Pay attention to accompanying signs suggesting detour options

• Don’t rely on guesswork—even a slight excess in height can cause crashes or serious damage

Visual Representation

• Two large black arrows, one pointing up and one down, symbolize vertical clearance

• The numeric value (3.9 m) is centered between the arrows

• Yellow background means caution or warning

Conclusion

The Maximum Height Clearance sign protects both infrastructure and road users from costly and dangerous collisions. It’s a must-know for commercial drivers and anyone operating a tall vehicle. Knowing how to interpret and respond to this sign isn’t just part of your G1 test—it’s vital for safe and legal driving in Ontario.