Public Transport Analysis

Transit can be studied from the perspective of demand (ridership), supply (service), and operation.

Global transit feed specification (GTFS) files and walk network data are the primary sources for creating the network and timetable used in transit analysis.

Transit demand can be estimated using regional travel demand models or simplified transit demand models. In both methods, the assignment process determines the number of passengers for each line. For small-scale studies, or those focused on a specific line, demand can also be estimated through other methods, such as utilizing online transit planning tools and studying similar lines.

In the context of transit modeling, assignment refers to the passengers’ selection of transit connections (transit departures/services boarded in a trip). During transit assignment, a search process identifies all available connections from an origin to a destination within the passenger's desired departure time. Infeasible connections, for example, those that are too long or involve too many transfers, are removed. The transit demand from origin to destination is then distributed among the feasible connections based on a choice model. Optionally, an iterative process can be added to the assignment to account for the capacity restrictions of transit vehicles. Depending on the assignment method, demand-responsive transportation (DRT), also known as on-demand service or micro-transit, and shared micro-mobility (e.g., e-scooter sharing) can also be modeled and analyzed.

It's worth mentioning that onboard travel surveys provide valuable information on rider demographics, trip purpose, and travel patterns. The results of these surveys are first validated based on the transit services and the feasibility of origin to destination paths (linked trips) using their composing legs (unlinked trips).

Transit service studies focus on how effectively an area is covered or serviced by the system:

• Stop catchment area analysis:

  A catchment area, also referred to as a service area or coverage area, is the region around a transit stop from which people can reasonably access that stop. The size of this area varies depending on the transit system, the availability of infrastructure like bike lanes, and the demographics of the population. Intersecting (overlapping) the catchment area with land use data helps to determine the number of people or attraction units (e.g., jobs, university seats) that can potentially be serviced by the system.

• Isochrones analysis:

  Also known as contour lines analysis, isochrones analysis involves calculating and mapping the travel time (or impedance) of traveling from one place to other locations (or traveling to one place from other locations), typically displayed with different colors. In this analysis, the focus is on the travel itself rather than the land uses at specific locations.

• Accessibility analysis:

  Accessibility is defined as the number of attraction units that can be reached from a given location within a reasonable amount of time. Both travel (service/timetable/departures) and land use are studied in accessibility analysis, which serves as a crucial measure of equity in transportation. To gain a greater understanding of the accessibility analysis, consider watching our in-depth webinar on this topic.

The type and size of the fleet can be determined through line blocking (vehicle scheduling). The outcome of this process is an optimal solution for allocating designed timetable departures to the fleet, which in turn helps determine procurement and operational costs.

Transit operation and their interactions with passengers, other vehicles, and intersection can be studied using micro-simulation modeling.

In this type of study, transit vehicles are coded with their departure times. Passengers interact realistically, reflecting crowded conditions, and resulting transit delays and/or passengers being unable to board. Intersection control methods (including transit signal priority, TSP) are precisely modeled.

This analysis can help achieve a realistic timetable design and improved system components such as vehicles, stations, and intersection control.