Integration of traffic data with navigation systems enables navigation systems to use traffic and other related data to optimise routing and travel times by taking into account traffic conditions and other disruptions to traffic flows. The integration may occur in a number of ways. For example, integrated automobile navigation systems use an on-board navigation system and cellular telephone. The navigation system would use the global positioning system (GPS) to position the automobile with respect to streets in a map database, to determine a route to the destination and to update the location as the automobile moves. A cellular telephone in the automobile may then communicate with a traffic information server to obtain travel times for each street segment of the route, which would then be used to refine the planned route, or to offer to the driver as an alternative. The cellular telephone can also be used to provide dynamic travel time information to the traffic information server, with each automobile in the system periodically transferring travel times for each segment that is traversed. The traffic information server would then analyse travel times to update travel time data for each street segment, which is then available to other users when they next connect to the traffic server. Other integration models exist. According to Consumer Reports, the data may be transmitted through Bluetooth, FM, or XM. In 2006, Clear Channel made a deal with BMW to supply traffic data for the carmaker's navigation units. According to GPS Review, the suppliers of traffic data to the navigation units get their own data from "road sensors, local departments of transportation, data collected from operators of large fleets of vehicles, and other manual sources such as traffic helicopters and listening to police scanners." Patents have been taken out for services that will collect movement data from GPS devices on the road to determine the current travel time between various points.
See also Waze
Real-time traffic estimation and dynamic route guidance With regards to the case of traffic estimation in real time, the traffic probes can be viewed as the observations obtained from the traffic sensors. The traffic estimation techniques are able to use the information of location and speed of the vehicles obtained using the GPS enabled mobile phones for traffic state estimation of highways. Work et al. utilized an algorithm known as "Ensemble Kalman Filtering" which uses the GPS data for traffic state estimation of highways. This technique was experimented by simulating the interstate 880 of California using 100 vehicles in Mobile Century experiment. In this way, the real-time traffic information may be utilized in the routing system for influencing the decision making process of routes. In the study of the performance of routing systems by Kanafani and Al-Deek, the routing system is evaluated using the concept of an ideal urban corridor consisting of a freeway and street network. Based on their findings, the guidance system was likely to achieve a reduction in travel time of 3-4% compared to the user equilibrium without guidance system. This level of reduction in travel time depended on some properties of the network. For instance, in cases where the speed of travel in the city streets was lower compared to the speed of freeway travel, a higher travel time reduction was obtained. However, extra information concerning traffic status is not always connected with better functioning of the transportation network under any circumstances. Thus, for instance, Ben-Akiva, de Palma, and Kaysi took into consideration the information gathering behavior of the drivers while developing the dynamic network model and suggested that the drivers’ information about the network may influence their route choice. It turned out that in this case, the accuracy of the information affects both positively and negatively the operation of the dynamic network model since it may influence the choice of routes and departure time of the drivers. Hence, the dynamic route guidance system needs to be evaluated not only in terms of information provided to the drivers but also in terms of its effects.
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