Calendar Exceptions allow you to precisely alter service in advance, such as anticipated holiday service suspension, or regularly-occurring modifications to existing service.
Calendar Exceptions Overview
When to Use Calendar Exceptions
Holidays and Planned Service Disruptions
The most frequent use for a Calendar Exception is to suspend or alter service for a holiday. Calendar Exceptions allow you to remove service entirely, swap out one Schedule for another (such as replacing weekday service with Saturday service,) or add service that is not otherwise available (such as a special shuttle for football games.)
Short-term or Sporadic Service Disruptions
Longer-term service changes, such as a long construction detour, should be managed using Calendars. A short-term service change (such as a single-day detour for a parade) are well suited for a Calendar Exception. If a disruption happens several times, but on different days of the week (such as four separate road repair closures), a Calendar Exception may be easier than creating many Service Periods.
Because Calendar Exceptions work on a principle of adding and removing service from Calendars, individual Routes and/or Trips within those Calendars cannot be exempted from the Exception. If a Calendar Exception should only affect a certain Trips and/or Routes, those Trips and/or Routes will need to be moved to their own Calendar from any existing Calendar they may be a part of.
Unscheduled Service Disruptions
GTFS is unable to accommodate short-notice service exceptions (such as bad weather or heavy traffic,) but is able to anticipate scheduled service disruptions, such as holidays or construction detours.
For more information on short-notice service disruptions, learn more about Trillium's Transit Alerts. Transit Alerts allow an agency to quickly broadcast service changes in real time, letting riders know about disruptions as they occur.