Discussion on Exceptions from today's Webinar

[Aaron Priven]

Hi. There were some questions about exceptions at today's Webinar. It
sounded like there wasn't complete understanding, and so I thought I
would go ahead and explain at least what our situation is at AC
Transit. I suspect other agencies have similar issues.

AC Transit has some supplemental service that's designed to serve
students at middle and high schools (although anyone can ride these
lines). These trips operate school days only. Some of these trips
operate on separate routes, numbered 600-699, while others run as
supplemental trips on our regular routes. (In the past there have
been situations where we have slightly different schedules on a
regular line for school days and non-school days. We don't have any of
those at the moment.)

In addition, to accommodate varying school schedules, some of these
school-day trips run at different times on *particular* school days.
(These are known as "Wacky Wednesday" trips because that has been the
usual day that schedules change, but this is not constant.)

All this is further complicated by the many different school schedules
that we have to cope with, at several private schools with specialized
service and at several different public school districts.

The Google Transit Feed Spec is designed to get information about
specific dates, in order for Google to create itineraries. In theory
we could specify all the school days for each different school ahead
of time and enter that into the scheduling system to create a
calendar_dates.txt file that includes exactly which runs operate on
which days. But we don't do that and I doubt we will begin; it's too
complicated and schools have a tendency of changing their schedules
without a lot of notice. Instead, we use "exceptions" to mark trips as
school days only or school minimum days only. That's what we put on
our public timetables. The calendar_dates.txt file is not able to deal
with this kind of information, so I suspect it would simply get lost,
and all the trips would show up as running all the time.

We also have some lines that run two days per week. This, at least,
can be clearly set in calendar.txt, although it would need to be
recognized by the timetable publisher program.

I hope this is helpful in understanding the questions that were asked
today.

I am grateful to you for making this tool available. I am certainly an
advocate for our using tools like this and also, whenever we can,
contributing back to the project.

Aaron Priven
Public Information Systems Coordinator, AC Transit

[Lenore Weiss]

Aaron:

To the best of my knowledge, we do not publish timetables for schools.
How close do you think this tool would get us in terms of our local and
transbay lines?

Lenore

Lenore Weiss
Web Administrator AC Transit
1600 Franklin Street
Oakland, CA 94612
(510) 891-7197 -- office
(510) 919-6817 -- mobile

[Joe Hughes]

Hi Aaron,

As someone who helps evolve the GTFS, I'd like to hear more about why
you think that "The calendar_dates.txt file is not able to deal
with this kind of information". If it's truly not able to represent
your use cases, then we should extend the format so that it can. Feel
free to reply privately.

I don't know the full details about your system, but it seems to me
that you could just define a separate service_id for the trips that
only run on school days, and then use calendar.txt and
calendar_dates.txt to define which days those are.

Thanks,
Joe Hughes

[Frank]

Hi Aaron,

Yeah, sorry that I butchered the answer to your question (there was
another question about addition service key types for generating
timetables for holidays and special service, which got my thinking
going in the calendar.txt direction).

Anyway, in TTPUB, there are a couple of ways to footnote trips:

1. Use a different service key for a certain day -- at TriMet, we have
Friday Only trips on a couple of routes. Eg:
http://trimet.org/schedules/new/w/t1100_0.htm#footnotes and
http://trimet.org/schedules/new/w/t1193_0.htm#footnotes.

2. Flag trips that are exceptions -- at TriMet, there are Express and
Limited stop trips that are exceptions, which are flaged with a
certain 'Trip Type' to differentiate them from other trips: Eg:
http://trimet.org/schedules/new/w/t1109_0.htm#footnotes and
http://trimet.org/schedules/new/w/t1031_0.htm#footnotes.

As you have noted, there is currently no mechanism to flag trips in
GTFS. That said, we can add anything we want to that format.
Further, we could even propose a change in GTFS to support this flag
(eg: http://groups.google.com/group/gtfs-changes/web/open-proposals)
as a formal part of the spec.

Action item for me: I'm going to fix the TTPUB code to read a new
field from GTFS's trips.txt called trip_type, and I'm going to get our
GTFS feed to include that field.

Thoughts? Would trip_type work (theoretically) for AC Transit? Does
AC Transit need to do anything more than footnote exception trips (at
least timetable-wise)?

--Frank

ps, please join this group...not only do we need people and discussion
here :-), it will also post your messages without moderator approval.

[T Sobota]

Aaron-

Metro Transit in Madison (aka Berkeley East) directly operates the
transit routes that serve the University of Wisconsin campus. The
schedule of these routes vary not only by day of week (runs later into
night on Friday versus Monday-Thursday), but also time of year (less
frequent during recess periods, more frequent during standard class
sessions) - and not to forget they follow their own holiday schedule
as to when they do not operate at all. Not having implemented the
Google trip planner to date, I cannot confirm my tinkering was correct
- but I do believe I had created at one time a valid feed that did
essentially require calendarizing the entire schedule pick period. It
defined every possible block/trip combination possible for the time
period involved on the campus routes (M-R recess, M-R standard, F
recess, F standard, etc., etc.), then assigned those blocks/trips to
each and every calendar day (or not, if it was a university holiday).
I would otherwise echo your experience with supplemental school day
service (masssive variation with minimal advance notice).

As Frank referenced - Metro Transit has also been inquiring about
additional (general) service types. We are not large enough of a
system to throw out our full Sunday schedule on holidays as well. We
publish four schedule types on a regular basis (weekday, saturday,
sunday, holiday), and have three additional schedule types we publish
specially for borderline holidays (MLK/Friday after Thanksgiving,
Christmas Eve & New Years Eve) - blending a Saturday schedule with
some additional weekday commuter routes.

As for TTPUB - our printed materials for the campus service actually
display two distinct weekday schedules (recess and standard), it would
be too complex to intermingle and footnote which trip was which on a
single schedule display. We would likely try to pursue that avenue in
implementing TTPUB. As for the service types - Frank has discussed
with me how to somewhat accomodate additional schedule types within
the current TTPUB app, but I continue to hope for a generous
programmer to contribute a fix/expansion of the service types
available beyond the current three.

--Tim Sobota