Abstract
Traffic engineering terminology is incomplete. Definitions are vague and ambiguous. Consequently the numerical evaluation of parameters has a restricted value. This applies particularly to the term capacity. In the current interpretation the value of this quantity is determined by the heterogeneity of the road user population, the bulk of vehicles and the road network. Even the discussion on the significance of technological developments for the promotion of homogeneous traffic flow and its effect on highway capacity is obscured as a result of the restricted validity of the capacity definition.