Dynamic Car Journey Planner
The basis of a static car journey planner is the digital map, which holds amongst other attributes the average travel speed on the road network. The integration of real-time data inside the trip calculation improves the results of the car journey planner significantly (see also Fig. 1)
The dynamic car journey planner of mdv can include
- speed profiles
- short and middle term traffic incidents
- current traffic situation (real-time and forecasting data)
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 Different data sources of a journey planner for the motorized indivdual transport |
Speed profiles
With the integration of speed profiles the journey planner can take into account the average traffic situation on the main street network depending on the time of day. Speed profiles are based on archived traffic data for the main street network and are calculated for different time periods of a day and different day types. The speed profiles could be updated in regular intervals. As an effect of the use of speed profiles the directions and travel times may vary during the day for an origin destination relation (see also Car Routing)
Short and middle term traffic incidents
The integration of traffic messages about roadworks and/or other incidents is another quality improvement in trip planning. Incident information has to be integrated by the trip planner during the running process. This means that the router retrieves the information in regular intervals and integrates it into the trip planning.
Another server process, called EFAITRealtime in the following figure, is responsible for the information retrieval from the different data providers. The retrieved traffic information is provided to the dynamic journey planner.
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 Short and middle noticed traffic incidents |
The format and the reference system of the traffic information is another point which has to be considered. The standard RDS-TMC is used Europe-wide and provides traffic information via radio. Information about road works, accidents and traffic jams are transferred and processed by onboard navigation systems.
But also other standards and self defined formats are capable for the exchange between a traffic control centre and the dynamic journey planner of mdv. Beside the traffic information also periodical returning traffic events (i. e. on Sunday no driving is allowed downtown) can be transferred to the car journey planner.
All retrieved information are processed by EFAITRealtime and send to the journey planner via CORBA. In defined intervals the journey planner updates these data and integrates it in the trip planning.
Another challenge is the correct mapping of the information on the road network of the journey planner. The traffic information has no use if it can not be assigned to an edge of the journey planner road network. This is the reason for the use of a mapping table, which transfers the information from different external reference system to the internal system of the journey planner.
Current traffic situation (Real-time and forecasting data)
Additional also real-time and forecasted data can be integrated into the journey planner. The traffic information shows the current traffic situations on the main road network for a very short term. Current and forecasted traffic situations can be taken directly form an online traffic model. It makes only sense to use this kind of traffic information, if a feedback channel for the user is available (i. e. SMS, WAP, call-back, ...). For an internet journey planner, without any feedback channel or personalisation, this traffic data source has no relevance. If the user starts his trip directly after planning it via the internet, the information is no longer valid, because the forecasting term is already pass.
Also for this data source the program EFAITRealtime can be used. The application gets current and forecasted data from the traffic model and provides it to the journey planner.
