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Transportation Research Board Paper 11-1317 Committee on Major Activity Center Circulation Systems (AP040) Maximization of PRT Station Capacity Martin Lowson John Hammersley ULTra PRT Ltd Ashville Park. Thornbury Bristol Bristol BS35 3UU England ABSTRACT Approaches to maximize the throughput of PRT stations under peak demand conditions are examined. Stations must be designed consistent with the limitations of the guideways they serve. It is shown that simple algebraic models can provide key insights into the design issues and limitations. The fundamental design requirement is to minimize the overall berth cycle time, including: door opening, passenger load or unload, door close time, trip initiation, and vehicle resupply. Measured data on the times for passenger loading on the ULTra vehicle are presented. Elapsed loading times were found to be dominated by the door opening times of 10 seconds. Passenger loading times, ignoring door opening and closing, are small, 4.4 seconds for 1 passenger and 8.2 seconds for 4. Unloading times reduce to 3.2 seconds for 1 passenger and 5.4 seconds for 4. These short times are consistent with published data on loading and unloading in other transit situations. Some possible station designs are shown. These have been designed to meet objectives of combining minimum size with maximum capacity. New station designs featuring forward rather than reversing berths provide a benefit in capacity at the expense of some increase in size. It is found that a 5 berth station with current levels of PRT technology can be expected to provide a capacity of 600 vehicles per hour, each loading 4 people. Delivered passenger clearance rates of one every 1.5 seconds compare favorably with bus loading rates of one every 2.5 seconds. INTRODUCTION A key issue in the practical use of Personal Rapid Transit systems is capacity. There are three key determinants to PRT capacity. First is the basic capacity of the guideway – this is governed by the headway allowed between vehicles. Typical present headways (defined in this paper as separation between identical points on successive vehicles) are 6 seconds, providing a capacity of 600 vehicles per hour per direction or 2400 passengers phpd assuming that each vehicle has a full load of 4 passengers. These figures are being delivered by the first systems to go into service at Heathrow Airport, England and Masdar City UAE. It is generally believed that it will be possible to improve these capacities by a factor of two or three as practical operating experience is gained and technical improvements are made to the key separation control systems. Several authors have suggested that PRT headways can be reduced to 1 second or below. This is not an unreasonable projection. Drivers on freeways already accept separations below 1 second at speeds above 70mph. Controlled vehicle to vehicle separations of 0.24 seconds at a speed of 60 mph were demonstrated in practice in the PATH trials on the San Diego freeway in 1997. This corresponds to a headway, as defined in the present paper, of 0.43 seconds. However there are significant difficulties in delivering this capability with sufficient safety to meet regulatory requirements. At present very short headways remains an aspiration for future PRT development, probably at least 10 years away from realization. TRB 2011 Annual Meeting Paper revised from original submittal.
