INTRODUCTION
Taxi service is of significant importance in metropolitan areas, however, even after decades of studies and improvements,
its operational efficiency is still not quite satisfactory (e.g., a taxi fleet would spend over 50% of time idling in
a typical day). The reason behind this inefficiency is how the taxi service is organized: in most cities, taxi services
are delivered either by pre-arranged pick-ups (e.g., Dial-aCab service in UK and Singapore), street pick-ups, or taxi
stand pick-ups. Although modern taxi-dispatch systems (e.g., see [1] and [2]) can satisfy pre-arranged pick-up requests very efficiently, significant portion of demands still have to be delivered by the latter two choices and they are highly
dynamic and variable. This is one of the main reasons why
taxi services are still delivered very inefficiently.