Communications of the ACM
Real-Time Taxi Dispatching -sing Global Positioning Systems
The Global Positioning System (GPS) has been used extensively to track vehicles and provide traffic and positional information for fleet management [14]. This article discusses the experience of three Singapore-based taxi companies that implemented the GPS-based Automatic Vehicle Location and Dispatch System (AVLDS) to effectively support taxi service management. The AVLDS enables these companiesComfort, CityCab, and Trans-Island Bus Servicesto achieve real-time dispatch operations and provide customers with multiple channels to reserve taxi services.
The AVLDS consists of differential GPS, wireless data communication systems, computerized dispatch systems, and interactive voice responses. There are a number of stations established in various locations in Singapore for the transmission of data between control center and taxis equipped with GPS antennae, receivers, and transmitters. The AVLDS can immediately detect the nearest taxi to a particular customer, and identify each vehicles route and location together with its coordinates of longitude and latitude. Hence, it enables real-time collaborative operations between call operators and individual taxi drivers.
As soon as the request for a taxi is conveyed to the control center, the system dispatches a taxi to the customer at the appointed time.
The dispatch process involves the transmission of a customers request for taxi service via wireless data communications to a pool of cab drivers located within 10km of the customer. This is a significant improvement over the radio-paging system previously used, which contacted drivers operating within 2.5km of the customer. If one of the drivers accepts the job, he responds to the control center by pressing a button on a display unit installed in his vehicle. However, if none of the drivers respond within 10 seconds, the system automatically searches for the next nearest vehicles and the job is dispatched again. Upon successful matching, the taxi number and expected time of arrival is relayed immediately to the customer. The expected time of arrival is relatively accurate, because the system has the capability to continuously compute the time required for the taxi to arrive at a particular destination.
The AVLDS offers great flexibility in advance reservations in that it provides a multiple-access platform enabling customers to reserve taxi services via various modes. For instance, Comfort CabLinkthe AVLDS used by Comfort Transportationconsists of a variety of access features. CabLink Dial-a-Cab is the most common access allowing customers to use a conventional telephone or wireless mobile phone to call operators directly for taxi reservation. Alternatively, one can use a fax machine to reserve a taxi through CabLink Fax-A-Cab.
A registered customer can make use of CabLink AutoCall to reserve a taxi by calling a dedicated Auto-Call hotline. An automated voice guides the customer to enter a PIN as well as pick-up location and destination. The request for service is processed automatically. The pick-up location appears on the display unit in the taxi that accepts the call, while the customer is provided with the taxi number and the approximate arrival time.
Taxi reservation is almost a hassle-free process to a registered customer. An account number and an individual PIN is given to ensure confidentiality and security. The system also enables the customer to preset regular destinations, for example, home and office, in the cab companys database. A usual pickup location can be instantly identified and selected by pressing a particular button.
Comfort PCDial is a facility that links a PC with the companys online CabLink. A customer is required to key in details such as name, time, pick-up address, the type of taxi, and the number of taxis required. As soon as the request for a taxi is conveyed to the control center, the system dispatches a taxi to the customer at the appointed time.
Taxi reservation can also be made through the CabLink Hot Buttona preset button on public phones that enable one to reserve a taxi without having to know the telephone number of the taxi company. CabLink TOT is an automatic taxi-calling machine installed at major shopping centers, hotels, and other commercial buildings with substantial taxi demand. CabLink TOT is linked to the AVLDS that can automatically search a taxi for the customer. Upon reservation confirmation, a summary is given on the display panel together with an audio message. At the same time, a ticket indicating taxi number, location, and estimated time of arrival is issued to the customer.
Ergonomic Interface
An ergonomic human-system interface should facilitate the effective operations of taxi dispatch. The factors related to the human-system interface in the present case include data presentation on the on-board LCD display unit, in-vehicle manual operations, and environmental influences. It is not uncommon for a driver to pay less attention to the road conditions when reading a message on the display unit. Consequently, his attention may shift away from the primary task of driving.
The driver might also need to read the message on the display under extremely bright light in certain circumstances. Therefore, the information conveyed to individual taxis should be brief and clear. The on-board display unit should also be installed close to the drivers forward field of view without interfering with the vehicles instrumentation. In addition, the operational procedure should be simplified because the control functions associated with the display unit might influence a drivers ability to interact with the system. Noise and vibrations also influence a driver ability to read the display and respond to a request for service. Even the steady engine noise might compete with audio alarms and messages. Hence, in order to draw the drivers attention toward the transmitted dispatch information, the audio output of impulse noises emitted in short bursts from the display unit must be adjusted appropriately. Because these factors considerably influence the vehicle dispatch operations, they must be handled ergonomically when designing and installing the on-board display unit.
Practical Implications
The three taxi companies discussed here employ about 50,000 taxi license holders to provide taxi services to customers in Singapore. The implementation of the AVLDS results in a considerable improvement in communications between call operators and taxi drivers because the system enables an operator to convey precise digital data to drivers. Misunderstandings between call operators and drivers can be eliminated. The system is also able to relay different zones to track vehicles, although it tends to circulate a job to those taxis within a limited distance to a customer. The increase in efficiency of the entire dispatch operations process has resulted in enhanced customer satisfaction.
The AVLDS improves the productivity of call operators because it enables more reservations to be processed with the same level of manpower. The standardization of data entry and data processing also enables an operator to manage several calls instead of only one within a specific time frame. As a result, more requests for taxi services can be accepted. In comparison to the traditional radio-paging system, the percentage of calls received and matched has increased significantly. In addition, taxi drivers have experienced a considerable increase in productivity as they can accommodate more customers. At the same time, the system enables them to optimize their daily operating costs by minimizing empty cruising. Moreover, the drivers can receive road information and route guidance because the geographical information system associated with the AVLDS consists of a comprehensive database of suburbs and streets in Singapore. It can also offer prompt assistance to drivers in case of emergencies because drivers can instantly inform their company through a hidden alarm switch activator connecting to the control center.
The AVLDS cultivates an effective real-time collaborative working environment for call operators and taxi drivers, which results in a considerable improvement of taxi services in terms of time required for reservation processing and vehicle dispatching. It also equips cab companies with comprehensive data for operations management and strategic planning. However, the ergonomics of the human-system interface together with the environmental factors in relation to dispatch operations must be examined in order to achieve the expected capacity of the system. This article should provide useful information to the management of taxi services in different environments. It should also provide practical implications to the application of GPS technology in facilitating other forms of service vehicle operations and enhancing supply chain efficiency.
References
1. Collier, W.C. and Weiland, R.J. Smart cars, smart highways. IEEE Spectrum 31, 4 (1994), 2733.
2. Compasscom integrates emergency vehicle location systems. Global Positioning & Navigation News 10, 23 (2000).
3. Jennewein, J. Lexus, Volvo launch GPS-based telematics in the US. Global Positioning & Navigation News 10, 19 (2000).
4. Solomon, J. Trafficmaster drives telematics in Europe. Global Positioning & Navigation News 10, 20 (2000).
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