Allocation Planning for Probe Taxi Devices Aimed at Minimizing Losses to Travel Time Information Users

In many cities, taxis equipped with global positioning system (GPS) devices are used as probe vehicles. However, there are cases when the data from such taxis are not suitable for use as traffic information because of long data polling intervals. There are also developing countries in which taxis are not equipped with GPS devices. In such cases, a probe vehicle system has to be established by allocating probe vehicle devices to taxi dispatch centers (TDCs). In this study, the authors analyze the efficient allocation of such probe vehicle devices to TDCs under the cost constraint and the assumption of independent link travel times, adopting a definition of efficiency based on the loss to travel time information users resulting from information errors. The travel time information obtained using a probe vehicle system is the sample mean of a statistical distribution and should be treated as a statistical variable. Thus, the information error, which leads to losses to information users, is also a statistical variable. The allocation problem minimizes such losses. The results from a case study show that the loss to information users changes with the time of day and among different city areas. It is also shown that probe devices should be evenly allocated among TDCs. If either the number of probe devices or the data collection period is limited, more probe devices should be allocated to the central urban area where the traffic is heavier.