No Universal Federal Letter Height
The federal rule requires contrasting markings that remain legible during daylight from 50 feet while the vehicle is stationary.
Visibility and sizing guide
USDOT Number Size Requirements
Federal USDOT rules use a visibility standard rather than one universal minimum character height. Learn how to choose practical dimensions.
Reviewed against official federal guidance
Practical USDOT Compliance Guidance
Size for the Vehicle
Measure the available flat area and choose enough height and spacing for the actual pickup, box truck, van or tractor cab.
Check Additional Rules
A state or specific operation may add a size requirement, so confirm every authority that applies before ordering.
Related compliance resources
Order Durable USDOT Lettering
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Customize online or call with your exact wording, vehicle color, available space, quantity, deadline and delivery ZIP code.