Two dynamic capacities of a simple stalls/aisle system were defined in laboratory report LR 221 as cin, the maximum sustained rate that cars could be parked and cout, the maximum rate that they could be unparked. These two parameters were determined by the dimensions, layout, etc (but not the number) of stalls and could be used in the design of tidal-flow car parks. The present report defined a new parameter cto, the turnover capacity (cars/h) of a simple stalls/aisle system, and shows it to be the ratio of product to sum of cin, cout. Furthermore, it is shown that if more than cto cars/h pass through the system, less that cto cars/h can be served. It has been found that every parking activity and every unparking activity in an aisle has associated with it an 'inhibiting period'; and that the number of activities (however mixed) in a given time is limited by the sum of the participants' inhibiting periods, regardless of the number of stalls in the aisle. Mean inhibiting periods for each kind of activity can be measured directly or can be estimated from regression equations relating inhibiting periods to area-per-car-space, stall-angle, percentage-reversing and pillar-location. The principle of summation of inhibiting periods has been validated by full-scale tests and by computer models. Most car parks consist of a number of stalls/aisle sections arranged in series/parallel combinations to form single or multiple systems. The report describes how maximum flows and turnovers may be estimated for well-known designs of multi-level car park and how non-standard layouts may be analysed. Some worked examples are given. An operational checklist is included in the appendices. (Author/publisher)
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