What is the minimum permissible tire tread depth for vehicles on the highway?

The minimum permissible tire tread depth for vehicles on the highway is crucial for ensuring safety and optimal performance. A tire tread depth of 2/3 of the original tread depth is a commonly accepted standard. This depth allows for effective water displacement, reducing the risk of hydroplaning, which is essential for maintaining traction and control on wet surfaces. Tires with adequate tread depth provide better grip during braking and cornering, which is vital for overall vehicle stability and safety.

When considering the other options, a depth of 1/3 of the tread or 1/2 of the tread may not provide sufficient grip, especially in adverse weather conditions. Full tread depth represents optimal performance and longevity but exceeds the minimum requirement. Therefore, 2/3 of tread depth strikes a balance between safety, performance, and regulatory compliance, making it the correct answer.