New Rule Proposal: Feed-wide error given certain threshold of scheduled Trips not being accounted for in Vehicle Positions feed

[evansiroky]

Summary:

An error should be raised whenever a "vast majority" of Trips that should be in service at the time a Trip Update feed was downloaded are not accounted for in the given VehiclePosition records in the Vehicle Positions feed after accounting for canceled trips noted in the Trip Updates feed.

Steps to reproduce:

Given a TripUpdate dataset
and a Vehicle Positions dataset downloaded close to the same time as the TripUpdate dataset
and their associated GTFS Schedule dataset
When the validator has compiled a list of all trips that should be currently in service
and has scanned through all TripUpdate entities in a Trip Updates feed to determine which trips have been canceled
and has scanned through all VehiclePosition entities in a Vehicle Positions feed
and does not find a "vast majority" of Trips that were expected to be in service and that were not cancelled or not being accounted for in the VehiclePosition records
Then the validator should raise an overall flag that the Vehicle Positions feed as a whole did not have a "vast majority" of Trips being accounted for in the Vehicle Positions feed.

Expected behavior:

The GTFS-Realtime Best Practices state:

Feeds should cover the vast majority of trips included in the companion static GTFS dataset. In particular, it should include data for high-density and high-traffic city areas and busy routes.

The GTFS Validator should flag when the "vast majority" of Trips were not accounted for at the time that the trips should have been in service.

Observed behavior:

An error or warning is not raised for this problem at this time.

etc

• This issue seeks to add more detailed scope to Cover most trips in GTFS Schedule #119.
• The definition of "vast majority" needs some kind of percentage given to it
• This issue may run into problems with batch-processing from multiple files as discussed in Clarify batch processing docs and behavior in context of multiple files, cross message rules (E047) #100