WHY CITIES SHOULD PLAN FOR EMPTY PARKING SPACES.

WHY CITIES SHOULD PLAN FOR EMPTY PARKING SPACES. The article on parking I cited yesterday describes Professor Donald Shoup’s “85% Rule.” Shoup says that cities should “charge whatever rates lead to about 85% of the spots being filled up at any given time, moving rates up or down as demand fluctuates. Portland, Oregon and Anchorage, Alaska have adopted the 85% guideline. A result of queuing theory is that if you want to avoid lines at supermarket checkout counters, you have to have some counters that idle some of the time. It drives some planners crazy to have some idle capacity. They think of assets going to waste. They want to add capacity only when 100% of capacity is being used. We have all been in lines at toll booths and supermarkets where this fallacy shows up. Imagine some of the reactions to seeing 15% of parking spaces empty (or more—the 85% is an average over fluctuating demand).