Fwd: [gtfs-changes] proposal: specifying CO2 emissions for transit routes

[Aaron Antrim]

Hi all:

I passed this question onto Michael Winkler, a Green Wheels advisory board member, and SCHATZ energy researcher.

His response is interesting: Essentially, on average, transit fuel efficiency is not fantastic, but that gains in efficiency are realized by adding more passengers, and that transit offers other benefits than fuel efficiency.  His response is much better and more complete, below.

If some agencies are particularly interested in having this comparison show up in Google Maps (maybe their ridership is high and can boast great fuel efficiency?), then providing this information may be useful, so I would support the proposed change for them.

But, as Michael brings up, comparing vehicle fuel efficiencies may not always be a good way of representing the value of transit.  This came up at the California Association for Coordinated Transportation conference last year when Dan Sperling from UC Davis Institute of Transportation Studies made a blanket statement transit is inefficient and we should develop more efficient vehicles for personal mobility.  He has a good point, especially for rural areas — but I disagreed with his broad approach.  In most cases, buses are going to run anyway, partially because they serve an important purpose for disabled or mobility-disadvantaged riders, so, even if they are not efficient, why not put more people on them?

In short, there are lots of compelling reasons to take transit (low cost being one of them).  Let's be careful not to highlight immediately reduced CO2 emissions too much as a benefit — because there's so much that goes into that discussion).

Okay, probably more than enough said.

Aaron

Begin forwarded message:

From: Michael <ml...@humboldt.edu>

Date: 10 September 2008 2:59:02 PM PDT

To: Aaron Antrim <aa...@arcatacommunity.org>

Subject: Re: Fwd: [gtfs-changes] proposal: specifying CO2 emissions for transit routes

Aaron:

This is a tricky issue. Nationwide, my memory of diesel bus energy efficiency is approximately 33 passenger-miles-per-gallon.
This is worse than 2 people in a car with average fuel efficiency. A nearly full bus with 50 passengers would typically
get 200 passenger-miles-per-gallon, much better than anything else but a full Prius.

Some of the major positive reasons for transit are equity and to promote compact land use, two areas that would not show up
in figures on average fuel efficiency or average CO2 emissions. The energy efficiency benefits of transit show up when you add passengers
to existing routes, not in figures on average efficiencies.

In economics terms what's relevant is the marginal fuel consumption and marginal CO2 emissions of each additional transit passenger.
I would estimate that the marginal fuel efficiency of each additional passenger of at least 50 passenger miles per gallon or 0.4 pounds of CO2 per mile.
I would use this kind of figure (explained in simple terms) rather than average miles per gallon or average CO2 emissions per mile, system-wide
or for each route. For instance you could say, "for the average driver taking transit for a year rather than driving can cut your share of commuting CO2 emissions by 60% and keep 500 pounds of
CO2 out of the atmosphere."

                                                                     Michael

Aaron Antrim wrote:

Michael:

I am not sure if you mentioned this in the past.  The topic of this forwarded email is adding a way of specifying CO2 emissions for transit routes and displaying that information (maybe compared with average figures for driving) in Google Transit.

The forwarded proposal contains questions about the best way to represent this.  I don't know if this question is interesting to you — if not, disregard — if so, I will forward your response to the gtfs-changes group.

Aaron

Begin forwarded message:

From: Joe Hughes <joe.hug...@gmail.com>

Date: 9 September 2008 10:31:23 PM PDT

To: Google Transit Feed Spec Changes <gtfs-c...@googlegroups.com>

Subject: [gtfs-changes] proposal: specifying CO2 emissions for transit routes

Reply-To: gtfs-c...@googlegroups.com

Summary:
Add a way for feed publishers to indicate the carbon dioxide emissions
of public transit routes.

Motivation:
Several agencies have expressed an interest providing CO2 emissions
information to riders, so that riders can compare the impact of taking
public transit to driving.  Carbon dioxide impact calculations are
still a tricky business, but it might be helpful to provide a rough
estimate as a first pass, especially if agencies can provide values
based on their local conditions.

Proposal:
The following field would be added to routes.txt:
--------------------------------
co2_per_km (optional):
The co2_per_km field allows the agency to specify how many grams of
carbon dioxide are emitted for each kilometer that a passenger travels
on this route.  The value should be an integer, and should reflect an
individual passenger's "share" of the emissions, rather than the total
emissions of the vehicle.  If no emissions information is available,
the field should be omitted or left blank (as a value of "0" indicates
a route with no carbon emissions).
--------------------------------

Discussion:
This is a value that's controversial and tricky to calculate.
Ideally, a passenger's "share" of the emissions would reflect how many
passengers are on the vehicle at that point, but realistically, most
applications aren't going to have such detailed information.
Providing a per-route average allows the agency to incorporate the
factors that they think are important based on their knowledge of
their operations.

Your thoughts?

Joe Hughes
Google