The Tour planning procedure links the demand, i.e. the generated trip requests, with the supply, i.e. the vehicle fleet and the pickup and dropoff points.
Two methods are available to solve the planning problem:
- Dispatcher
The dispatcher does not know the trip requests until the moment they arise and tries to serve them with the existing vehicles. The selection of the vehicles depends on the spatial proximity, the boundary conditions of the passengers already in the vehicles and the detours to be expected.
The dispatcher is based on the routing-enabled network of the transport model, i.e. on the opened links and turns of its PrT reference transport system.
The dispatcher takes into account trip requests reserved in advance, such as trip requests with a pre-booking time of more than 30 min. Repeated optimization of the tour plans is necessary for the optimal combination of short-term and long-term planned trip requests. This task is performed by the tour planner. The allocation of trip requests to tours is thus always adapted to the information known at the time. The more often the optimization is performed, the better the result. Please note that many optimizations extend the run time of the procedure.
- Tour planning
Not all trip requests are known prior to tour planning. This would lead to a too optimistic planning basis. Therefore, the tour planning issue is divided into time slices that allow you to model the dynamics of incoming trip requests. The tour planner only uses the trip requests known in the current time slice for scheduling vehicle utilization. The vehicle positions are adopted from the current or previous time slice. A rescheduling of the travel requests for the change of time slices occurs either on the basis of the starting point of the current transports (optimistic) or on the basis of the arrivals (pessimistic).
Tour planning is based on skim matrices that have been calculated using the transport supply of conventional PrT. Tours are optimized using trip distances and travel times. The procedure uses traffic zones as a basis, but corrects the actual travel times and distances by comparing their spatial locations and zone centroids.
Optimization aims at meeting as many trip requests as possible, within the temporal and spatial restrictions defined, and using a minimum number of vehicles.
The dispatcher is based on the routing-enabled network of the transport model, i.e. on the opened links and turns of its PrT reference transport system.
The dispatcher takes into account trip requests reserved in advance, such as trip requests with a pre-booking time of more than 30 min. Repeated optimization of the tour plans is necessary for the optimal combination of short-term and long-term planned trip requests. This task is performed by the tour planner. The allocation of trip requests to tours is thus always adapted to the information known at the time. The more often the optimization is performed, the better the result. Please note that many optimizations extend the run time of the procedure.
Tour planning results
The tour plan calculated is aggregated in various ways and adopted into the transport model.
The paths of the passengers are saved as PuT paths. Each path contains three path legs: one arrival path, one departure path and the path leg calculated that was covered using the responsive transport system. This path leg represents both the possible detour as well as the wait time for dropping off or picking up other passengers. From the total of these paths, skims are derived, analogous to conventional PuT.
For adjacent zones, the random distribution of trip requests at the node level can result in trip requests receiving the same pickup as well as dropoff point. These special cases are then represented by a public transport path composed only of walk links. The passengers with this trip request reach their destination this way. The tour planning of the fleet, however, remains unaffected by such pure walk links.
Due to the stochastic disaggregation of the trip requests, skims should only be used after multiple calculations of tour planning, taking into account various seed random numbers for trip request generation.
In addition, the trips of each vehicle are saved to a specified path set. They are used as a basis for estimating the operating expenses. PrT paths are created gradually by servicing pickup and dropoff points. The paths between these nodes are determined via a shortest path search. The resulting volume can be saved as a link attribute.
The individual pickup or dropoff points of a tour can be linked to a zone, just as for trip request generation via shortest path search. This allows you to create a PrT demand matrix that consists of individual legs of the tour. The subsequent assignment of such a matrix to an existing network creates a more realistic picture of the network volume generated through demand responsive transport.
