By default, a regional analysis in Conveyal calculates accessibility indicators for every point in a grid.
You can instead request CSV files with accessibility, travel-time, or path detail results for specified origins and destinations at exact coordinates:
- Upload a CSV file and process it as a freeform (non-grid) spatial dataset. Time and path detail analyses are currently limited to 4 million destinations, and 16 million total origin-destination pairs. If a many-to-many analysis would exceed these limits and you need travel times only for linked pairs of origin-destination coordinates, you can use the "Linked origin-destination pairs" setting described below.
- Create a regional analysis with Origin points set to a freeform spatial dataset.
- Activate your desired analysis types in the "Record results" section, as described in the sections below.
- The maximum cutoff value will clip results, so set it to 120 minutes if you want full results for trips up to 2 hours.
Once a regional analysis with freeform origins is complete, you will have options to download CSV files of the results. These features are still experimental; contact your support team for more information.
The "Accessibility" checkbox (activated by default when configuring a regional analysis with freeform origins) results in a CSV file with a row for each origin point, destination opportunity layer, travel time percentile, and cutoff.
Travel time matrix
Activating "Times" (after selecting freeform (non-grid) spatial datasets for origins and destinations) produces a CSV file with a row for each origin point, destination point, and travel time percentile.
In travel time CSV results, a time of -1 indicates the destination is unreachable within the maximum cutoff specified when the regional analysis was created.
|Cambridge||Cambridge Family Health||5||9|
|Cambridge||Chelsea High School||5||44|
|Cambridge||Cambridge Family Health||50||12|
|Cambridge||Chelsea High School||50||56|
|Cambridge||Cambridge Family Health||95||12|
|Cambridge||Chelsea High School||95||-1|
|South Boston||Cambridge Family Health||5||36|
|South Boston||Chelsea High School||5||50|
|South Boston||Cambridge Family Health||50||41|
|South Boston||Chelsea High School||50||55|
|South Boston||Cambridge Family Health||95||46|
|South Boston||Chelsea High School||95||-1|
Activating "Paths" (after selecting freeform (non-grid) spatial datasets for origins and destinations) produces a CSV file with the following columns:
- origin: Id of the origin point
- destination: Id of the destination point
- routes: pipe separated list of GTFS routeIds, one per transit leg
- boardStops: pipe separated list of GTFS stopIds, one per transit leg
- alightStops : pipe separated list of GTFS stopIds, one per transit leg
- rideTimes: pipe separated list of in-vehicle travel times (minutes), one per transit leg.
- accessTime: walking time from origin to boarding stop of first transit leg (minutes)
- egressTime: walking time from alighting stop of last transit leg to destination (minutes)
- transferTime: time spent walking between transit stops for transfers (minutes)
- waitTimes: pipe separated list of waiting time (minutes) to board each transit leg, for the specific itinerary following this path that has the lowest waiting time
- totalTime: total time (minutes), for the specific itinerary following this path that has the minimum total time. Because all other components of travel time are fixed for a given path, the itinerary with the lowest waiting time should also be the one with the lowest total time.
- nIterations: number of departure minutes in the departure time window at which this path is optimal. Note the nIterations for each OD pair should sum to the number of total iterations, unless specific departure times result in total travel times that exceed the maximum cutoff.
Linked origin-destination pairs
You can save CSV time or path results for specific matched pairs of origins and destinations, rather than all combinations of origins and destinations.
To enable this feature, activate "Linked origin-destination pairs" in the regional analysis creation box. Ensure that the origin points and destination layer are from source files with corresponding rows (and therefore have equal numbers of points). This approach can greatly reduce the size of output files, restricting them to only a small set of OD pairs you care about. But it may not reduce compute time (which is primarily affected by the number of origins). If origin coordinates are repeated for different destinations, leaving this option unchecked will likely be faster even if you do not need all combinations of origins and destinations.
To prepare travel time surfaces, isochrones, or accessibility results for specific sets of origins using Python scripts, see the notebook in this repository. This notebook is provided as an example only, and Conveyal provides no guarantee of ongoing API compatibility for such external scripts.