public-transport/gtfs-utils

optimise-services-and-exceptions: analyse distribution of service dates -> truncate/expand time span

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#41 opened on Feb 28, 2022

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Description

As of gtfs-utils@5.1.0, optimise-services-and-exceptions.js implements a very rudimental optimisation strategy:

  • it calculates all service dates (both "regular" & exception_type=1-based) of a service, and then
  • checks if there are more "regular" than exception-based dates (in this case, it sets the respective daw of the week (DoW) flag to 1), or vice versa.

There is a lot of potential in changing the time span (start_date/end_date) of the service, so that the number of exceptions necessary to express it is minimised. To do this, we must consider the distribution of the service's dates, so that rare outliers – e.g. Christmas with a service that only runs during summer & on Christmas – are expressed as exceptions, whereas the majority of the dates is express using DoW flags.

Contributor guide

Research direction
Analyze the distribution of service dates to determine how to truncate/expand the time span, minimizing exceptions.
Tech stack
javascript
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50