The share of people living in cities is increasing worldwide. This makes public space in cities a scarce good. Subsequently not only the challenges in the transport system are increasing but also the availability and distribution of public space is a crucial aspect. Pedestrian priority zones, strolling or encounter zones and road designs such as shared space are a first attempt to tackle the exclusive claim of space by one single transport mode, which was predominantly the car in the recent decades. For example the concept of public long-term parking contradicts the flexible use of public space by reserving it for one mode; therefore space reserved solely for the car should consequently be reduced. One attempt to promote walking as a transport mode is the claim for minimum widths of newly constructed or rebuilt pavements. This is already established in the current Viennese planning guidelines. Still the question remains if this quality indicator is sufficient and how it should be dealt with for spaces where no physical cut-off by a kerbstone between road and pavement exists. Therefore in this paper we recommend the adoption of a new indicator – called “spacetime” (space multiplied by time, m²h). This new indicator takes into account a more flexible allocation of space for new road designs that consider the needs of non-motorized traffic such as shared space. We show that a short temporal impairment of quality for some road users can be accepted if a significant increase of space efficiency and traffic quality for the eco-modes (walking, cycling and public transport) is achieved overall. Depending on the occupancy rate and quality of infrastructure, the efficiency of “space-time” can serve as an empirical basis for prioritizing transport modes and urban transport policy measures.

Public space; indicators; efficiency; space-time