design speed

Meanings

1. Of a transport system (such as a road or railway), the assumed vehicle speed used in calculations when designing the system; typically the fastest speed at which it is deemed safe to use the system.
2. Of something that moves (such as a vehicle or motor), the optimal speed as endorsed by its designers; typically in terms of some balance of various factors that are relevant to the object's purpose, such as longevity, efficiency and velocity.