Request for Comment: Measurement of Service Bunching (Update 2)

Updated October 11, 2018

An updated set of charts has been added which show the evolution of headway values across the route by time of day, including an improved version of the “box and whisker” chart format. Scroll down to the end for this update.

Updated October 9, 2018

A substantial section has been added to this article with replies to many of the issues received in the comments and examples of revised and additional charts. Thanks to all who have commented on this.

Errata

I noticed that the data for the period from 6-7 am on 505 Dundas at Broadview Station has an unusually high value for headways below two minutes. On investigation I discovered that this was caused by garage trips that were inadvertently included in regular service. This only happens for buses that arrive via Danforth rather than via Broadview because of the geometry of the screenline in my model at Broadview/Danforth. This caused these trips to be counted twice: once on the way into service, and again when they left Broadview Station. Charts in the original article that were affected by this problem have been replaced.

Original Article

An ongoing issue for transit riders is the question of service regularity. TTC Service Standards call for vehicles to leave terminals no more than one minute early and no more than five minutes late. That by itself provides a huge amount of variation within “acceptable” service, but there is no attempt to measure route behaviour once vehicles leave the terminals.

One unfortunate effect of Andy Byford’s term at the TTC was the creation of service metrics without necessarily making things better for riders.

Riders do not care if a bus or streetcar is “on time” on many routes, only that they show up regularly. That is the whole idea of “frequent service” – you don’t need a timetable, you just show up and travel without an excessive, unpredictable wait.

I have been wrestling with how to illustrate the problem for some time. As part of preparation for a series on suburban bus service, I wanted to create a measurement that would be fairly easy to understand and which would allow comparison from route to route and place to place.

This article presents the work-in-progress for suggestions to improve or add to the charts before I start publishing data for many routes.

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