The simulation of public transport vehicles is optional. The prerequisite is that a timetable is available in the model. Vehicles of active vehicle journey sections are simulated whose start time is within the assignment time period. Public transport vehicles enter the network at the first stop point of the vehicle journey section and leave the network at the last stop point.
Behavior of public transport vehicles
Public transport vehicles behave like private transport vehicles, i.e. in order to follow their line route, lanes and lane turns must be permitted for the corresponding transport systems. Signal controllers at intersections is taken into account. For links reserved exclusively for public transport, it must be ensured that inbound and outbound turns have HCM-compliant turn types and that the signal controllers are adapted at the affected intersections if necessary, e.g. signal times are added.
The minimum of the link speed v0 in the unloaded network and the link type attribute vDefault-PuTSys() is used as the desired speed of public transport vehicles.
Stop times and slack time fraction
The stop times of the timetable are adhered to. You use the Slack time fraction assignment parameter to define the extent to which the departure time at a stop point may deviate from the timetable:
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With a value of 1, a public transport vehicle does not depart from the respective stop points before the scheduled departure time.
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With a value of 0, only the stop time is adhered to, but the timetable is otherwise neglected.
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A value between 0 and 1 can be used to simulate early arrivals.
Delayed public transport vehicles stop according to the stop time of the timetable and then continue their journey. The value of the Slack time fraction parameter has no effect in this case.
Modeling of stop points
It is recommended to model stop points as directed link stop points. The position and length of the stop points can be adjusted using the following attributes:
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Length
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Is stop bay
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Lane key
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Lane key opposite direction (for undirected stop points)
For undirected stop points, the attribute values Length and Is stop bay apply for both directions. The attributes Lane key and Lane key opposite direction are only relevant if the stop point is not a stop bay. Stop bays are always in the outermost lane.
Link stop points can be located on pockets. Stop points that are located on nodes are placed behind the node in the SBA graph depending on the vehicle journeys using them. More precisely, this means that if elements of the node geometry exist, for example a pocket on an outbound link, the stop points are located on lanes behind this pocket.
The number of public transport vehicles that can stop at a stop point at the same time depends on the length of the stop point and the effective vehicle length of the public transport vehicles. If the stop point is longer than the effective vehicle length of the first stopping public transport vehicle, a second vehicle can stop at this stop point, even if it no longer fits in completely.
Overtaking stopping public transport vehicles
Public transport vehicles can be overtaken when stopping under the following conditions:
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The public transport vehicle stops in a stop bay,
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the link on which the stop point is located has several lanes and these are approved for the corresponding transport systems.
This also means that a public transport vehicle arriving later with a shorter stop time can overtake a public transport vehicle that has already stopped. As a result, overtaking is not possible on single-lane links and links with a separate lane for public transport systems if the stop point is not a stop bay.
Measurements from simulated vehicle journeys
If public transport vehicles are also simulated, the simulated times of the last iteration are automatically saved in the following vehicle journey item attributes:
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Measured arrival (1)
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Measured departure (1)
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Measured post run time (1)
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Measured stop time (1)
In addition, the calculated attributes Measured delay at arrival (1) and Measured delay at departure (1) are output. These attributes are overwritten when the assignment is executed again. If the vehicle journey sections are restricted to active items, only the values of the vehicle journey items for whose journeys at least one active vehicle journey section exists are reset. In any case, only those values are deleted that fall within the simulation period, i.e. the assignment time period plus the post-assignment period.
The measured data allows both a comparison with the timetable and the testing of alternative scenarios. Deviations from the timetable can be displayed graphically, for example in the network editor or in the graphical timetable, or in tabular form. A special function can be used to generate vehicle journeys from measured vehicle journey item data. In this way, the vehicle journeys simulated in SBA can be tested with regard to their effects, for example in relation to the demand calculation or to a public transport assignment result.
Main nodes
The following notes apply if main nodes exist in the model:
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Main turns may also have to be permitted for public transport systems.
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Stop points that lie within main nodes are ignored. Depending on the direction of the affected vehicle journeys, you may have to multiply these and place them on links before or after the main node. This may also require the rerouting of affected line routes.
