The Public Transit evaluator calculates the travel time along a public transit line segment based on the scheduled public transit service. The travel time returned includes the wait time until the next scheduled transit trip begins plus the travel time along the transit line segment from one end to the other. Use this evaluator to model people traveling by public transit. It's not designed to model the travel time of buses driving along roads.
The Public Transit evaluator is only available for time-based cost attributes on edge sources called LineVariantElements when the network dataset's feature dataset and geodatabase contain all the feature classes and tables required by the Network Analyst public transit data model.
The Network Analyst solvers perform a graph search through the edges of the network dataset. When a solver encounters an edge that's configured to use the Public Transit evaluator, the Public Transit evaluator performs a calculation to determine the travel time to traverse that edge. The evaluator calculates the travel time by considering the time of day the edge was reached and querying the public transit schedules stored in the public transit data model tables to find the most efficient transit trip available. The travel time cost returned by the evaluator is the sum of the wait time until the transit service along the line begins and the time for the transit service to travel from one end of the edge to the other.
For example, suppose the traveler reaches the edge at 8:06 a.m. The scheduled bus service begins at 8:10 a.m. and takes five minutes to travel to the next stop. The evaluator will return a travel time of nine minutes, because the traveler must wait four minutes for the bus service to begin, and then ride the bus for five minutes to reach the next stop.
The evaluator always chooses the most efficient service, which is the service that reaches the terminating stop earliest, subject to any service constraints from attribute parameters or analysis dates. For network analysis calculations that treat the time of day as the arrival time, the evaluator chooses the service that departs the originating stop latest.
Traversal of the transit line in the backward direction (against the direction of digitization) is prohibited. The evaluator returns a value indicating that travel in this direction is restricted.
It's not currently possible to limit the number of transfers used by the traveler.
Analysis dates and times
When querying the public transit schedules, the Public Transit evaluator will consider the weekday or date and time the transit line is reached. Only transit service that operates on this weekday or date will be considered. If an analysis date and time of day are not specified, network edges that use the Public Transit evaluator will be treated as restricted.
If the analysis date is a generic weekday, such as Wednesday, all regular service that operates on Wednesdays, as defined in the Calendars public transit data model table will be considered. Service added or removed on specific dates using the CalendarExceptions table is ignored when using a generic weekday, and the date range specified in the Calendars table is also ignored.
If the analysis date is a specific date, all public transit service operating on that specific date will be considered. This includes regular service defined in the Calendars table if the analysis date falls within the date range specified there as well as exceptions to the regular service defined in the CalendarExceptions table.
Sometimes, public transit service along a particular line begins late at night and continues running past midnight into the early hours of the next morning. If the analysis time is early in the morning, service of this type that is still operating from the previous day will be considered. If the analysis time is late at night, service spanning midnight will be considered, and service beginning in the early hours of the following morning will also be used.
For cost attributes that use the Public Transit evaluator, you can optionally define one or more attribute parameters that further control the behavior of the evaluator. For example, you can use an attribute parameter to exclude transit service that is not wheelchair accessible. The supported parameters are listed in the table below. They must have the exact names and types listed in the table.
Supported attribute parameters
This parameter excludes particular transit lines or routes from the analysis. For example, you could use this parameter to model a temporary subway line closure or the elimination of a bus line.
This parameter should be formatted as a space-separated string of ID field values from your Lines table. For example, to exclude bus lines 2 and 6, set the parameter to 2 6.
This parameter excludes particular modes of public transit from the analysis. For example, you could temporarily prevent travel on all subway lines to model a full subway system closure or worker strike, but leave all bus lines in operation.
This parameter should be formatted as a space-separated string of GRouteType field values from your Lines table. For example, to exclude subway or metro lines, set the parameter to 1. To exclude both subway and bus lines, use the space-separated string 1 3.
The supported modes are listed in Network Analyst public transit data model.
This parameter excludes particular transit runs from the analysis. For example, you could use this parameter to model cutting service after a certain time of day or eliminating some runs along a line while retaining other runs.
This parameter should be formatted as a space-separated string of ID field values from your Runs table. For example, to exclude only run 12, set the parameter to 12. To exclude runs 12 and 16, set the parameter to 12 16.
Traveling with a bicycle
When set to True, this parameter indicates that the traveler is traveling with a bicycle. Transit service on which bicycles are not allowed, as defined by the GBikesAllowed field in the Runs table, will be excluded.
This parameter applies only to public transit line edges in the network dataset. To model travelers riding bicycles along streets, separately configure the evaluators for your impedance attribute's street edges to appropriately calculate the bicycle travel time along streets.
If the Runs table does not include the GBikesAllowed field, this parameter is ignored, and bicycles will be considered allowed on all runs.
Traveling with a wheelchair
When set to True, this parameter indicates that the traveler is traveling with a wheelchair. Transit service that is not wheelchair accessible, as defined by the GWheelchairAccessible field in the Runs table, will be excluded.
This parameter applies only to public transit line edges in the network dataset. You must separately handle wheelchair accessibility for stops and stations by, for example, creating a restriction attribute that uses the GWheelchairBoarding field in the Stops, StopsOnStreets, and StopConnectors data model feature classes.
If the Runs table does not include the GWheelchairBoarding field, this parameter is ignored, and wheelchairs will be considered allowed on all runs.
Network edges that use the Public Transit evaluator should not be considered apportionable, meaning that you cannot model traveling only part of the way along one of these lines. The evaluator can only accurately return the complete travel time required to travel from one end of the line to the other. It does not accurately estimate the time to travel to a point part of the way along the line. This is because the travel time is calculated entirely from the schedules, not from the line's geometry.
Because of this, network analysis input points such as stops or facilities should not locate on transit lines. These should locate on streets, and travelers should access the transit lines only by walking to a stop and boarding the transit service at the stop. Network Analyst automatically prevents network analysis inputs from locating on network edges that use the Public Transit evaluator.
Barriers also cannot be located on network edges that use the Public Transit evaluator. To temporarily suspend service along a transit line, use one of the attribute parameters listed in the table above.
Travel time along transit lines that use the Public Transit evaluator is calculated entirely from the schedules, not from the line's geometry. The lines are not considered to be a true representation of the paths taken by transit vehicles. Furthermore, travelers using scheduled public transit service are limited to boarding and exiting the transit service at the locations of stops. They cannot exit a moving bus or train between stops.
A service area polygon is intended to represent the area reachable within a given time or distance limit from a particular location. Since transit lines are not necessarily geographically accurate and since passengers can only exit at stops, service area polygons should not be generated around traversed public transit lines. The area directly adjacent to a line is not reachable unless the traveler can exit at a stop and walk along the same street within the time limit. By default, Network Analyst automatically excludes from service area polygon generation network edges that use the Public Transit evaluator. The transit lines are still used in the analysis, and you may see them in the service area line output, but polygons will not be generated around them.
Your output service area polygons may include multipart features showing seemingly disconnected areas around transit stops or stations. This is expected and correct. If you're creating a 30-minute service area, your traveler could exit the train at a station after traveling for 25 minutes and walk for 5 minutes, or they could continue traveling and exit the train at the next station after 28 minutes and have only 2 minutes remaining for walking. However, since trains typically go faster than people walk, the walking traveler could not reach all the areas between the two stations without exceeding the 30-minute travel time limit. Consequently, a small area around each station is reachable within 30 minutes, but much of the area between the stations is not, and the 30-minute Service Area polygon will contain each of these disconnected areas surrounding the reachable stations.