Whats the difference between a 20mph speed limit and a 20mph zone?
A 20mph speed limit is indicated by entry signs to the area subject to the 20mph limits in addition to smaller repeater signs. The repeater signs are a requirement for a speed limit based approach. A 20mph zone has signs at the entry points together with suitable traffic calming measures to provide a self-enforcing element, but does not include any repeater signs.