An Estimator component has the purpose to analyze a certain propose mode (in a trip-based model) or a chain of modes (in a tour-based model) and assign a certain utility to it. Later on, this utility can be used to make an educated guess about which alternative should be chosen.
The DMC extension contains a number of predefined Estimator implementations, but it is also possible to write custom ones. How to do that is explained in Customizing the model.
In the following the existing built-in estimators are described. Some of them exist in a trip-based and tour-based version, some only in one. While some of them have additional configuration options that can be defined in a parameterset, some don't. In any case, the estimator can be chosen in the main config group. For a trip-based model, the estimator can be defined as tripEstimator, while for a tour-based model it needs to be set in the tourEstimator parameter. Depending on which model type is used, the respective field is active:
<module name="DiscreteModeChoice">
<!-- Defines which TourEstimator component to use. Built-in choices: ... -->
<param name="tourEstimator" value="Cumulative" />
<!-- Defines which TripEstimator component to use. Built-in choices: ... -->
<param name="tripEstimator" value="Uniform" />
<!-- Trips tested with the modes listed here will be cached for each combination of trip and agent during one replanning pass. -->
<param name="cachedModes" value="car, pt, ..." />
</module>The cachedModes parameter defines which trip estimates should be cached. This is especially useful in a tour-based set-up. If estimates are not cached, trips are re-routed for each possible tour. If they are cached, one and the same trip (with the same mode) reuses one estimate in any tour that it is part of.
Description: The Cumulative tour estimator is a special estimator that does not perform any estimation on its own. Instead if look up the estimator given in tripEstimator and applies it to each trip in a tour independently. Finally, the utilities of the single trips are summed up.
Level: Tour
Configuration:
No specific configuration available. The tripEstimator field from the main DMC configuration is used.
Description: The MATSimTripScoring trip estimator approximates the MATSim scoring function. Internally, the considered trip is routed using MATSim's TripRouter component. Afterwards, the scoring parameters defined in the respective calcScore config group are applied. Since the at the time of replanning the exact resulting departure and travel time is not known completely, this is only an approximation.
Level: Trip
Configuration:
No specific configuration is available. The parameters from calcScore are used.
Description: The MATSimDayScoring tour estimator approximates the MATSim scoring function, similar to the MATSimTripScoring esimator, on which it builds. Two improvement are included that make use of the tour-based character: Using the initial departure time of the tour and the estimated travel times, delays can be predicted and considered to certain extent. Also, day-based scoring parameters such as daily costs are considered in this estimator. Again, it only approximates the score accumulated by trips throughout the considered day, but not the score resulting from activities. In principle, this would be possible, so here we consider it as future work. Note that day-based scoring parameters are considered. Therefore, the estimator should mainly be used in a plan-based context (except those parameters can be expected to be zero).
Level: Tour (preferrable plan-based setup)
Configuration:
No specific configuration is available. The parameters from calcScore are used.
Description: The Uniform selector returns 1.0 for any alternative that it encounters. Therefore, each altenratives obtaines the same valuation.
Level: Tour or Trip
Configuration: No specific configuration is available.