What Is It?

• Route guidance is used in many contexts: in transit and commercial fleets that track vehicles and dispatch drivers using wireless location technologies such as beacons, microwave signals or satellites; on talking buses and trains that announce destinations automatically; in platform and station signs that give riders real-time information; and in train dispatch and control systems. Increasingly, however, route guidance is coming to refer to systems that communicate information about a route to the driver of a vehicle, usually through an on-board device. This section addresses this last type of route guidance, also known as in-vehicle route guidance.
• It is comprised of: a digital map database; a system that synthesizes signals or sensor data to locate the vehicle on a map; a route planning function that designs a path before or during a trip, according to pre-selected criteria or preferences; a route guidance function, which directs the driver along the planned route; a device or devices that serve as an interface between the human user and the system; and a one- or two-way wireless communication system.
• Systems can use either static or dynamic databases. In static systems, the information is usually pre-loaded on a high-capacity storage device, such as a CD-ROM or DVD, that can be accessed by the driver. In dynamic systems, information is conveyed over a continuous, two-way communications link to an on-board device that recommends to the driver a "best" route, according to pre-selected criteria. See our Telecommunications Diagram on In-Vehicle Route Guidance for more information.

• Modern route guidance systems rely on sophisticated location and navigation technologies. For these to function properly, they must have access to a large volume of accurate, real-time traffic and road condition data. They must also have a robust, stable architecture and be able to interact seamlessly with numerous different components. The architecture must also allow for frequent system upgrades and evolutions. Another critical challenge is integrating map databases with one another.
• Many human factors issues remain to be resolved concerning the functionality and safety of route guidance systems that drivers use while they are operating a vehicle.
• The market forces driving the design of a navigation system are affected by cultural expectations, environments and driving patterns, making it unlikely that it is economically feasible to develop a single system that can satisfy them all well.

• Route guidance systems are intended to enable a driver to take the route that most closely matches his requirements. Usually, this means the one that is shortest, fastest or least congested (or some combination of those).
• Ideally, the route guidance system will be robust enough to help drivers disperse themselves efficiently so that they fully utilize all available routes. Otherwise, there is a danger of simply transferring the congestion from one portion of the transportation network to another.

• Route guidance is most widely used in Japan, in part because of the dearth of workable street addresses and names there. Maps with landmarks and prominent geographic features are stored on-board the vehicle for the driver to access.
• Systems popular in Europe use devices that receive information broadcast over radio frequencies and suggest alternatives based on real-time conditions.
• In the U.S. drivers do not place a high value on location information. Instead, the most popular devices are Mayday systems that connect the driver to a central service bureau in the event of an accident, mechanical trouble or safety threat.

Author: Phyllis Orrick