Transcript Evaluating the Efficiency of Mass Transit

Evaluating the Efficiency of
Mass Transit
Group 4
Liles, Daniels, Garcia, Cannon, Valencia
PHYS 1303 – Earth’s Changing Environment
Dr. Loxsom
Presented on April 28, 2004
Environmentalists’ Claim
Mass transit is cleaner, more efficient

NO2
– Cars: 2.06 g/pm
– Bus: 1.54 g/pm
– Rail: 0.47 g/pm

CO / Hydrocarbons
– CO Cars: 15.06 g/pm
– CO Bus: 3.05 g/pm
– CO Rail: 0.02 g/pm
– Hydro Cars: 2.09 g/pm
– Hydro Bus: 0.2 g/pm
– Hydro Rail: 0.01 g/pm
Environmentalists’ Claim (cont’d)
A bus with as few as 7 passengers is more
efficient than an auto
 Bus is 6 times more efficient than auto
 Rail is 15 times more efficient than auto

A single person using transit could save 200
gallons of gasoline/yr
 A 10% nationwide increase would save 135
million gallons of gasoline/yr

Towards a Critique
True, autos are the major source of pollution
 But, the data, when correctly interpreted
does not suggest that mass transit is the
answer
 Buses, streetcars, and rail, use energy,
generate pollution, and have other impacts
 Public transit might actually aggravate
existing problems

Load Factors



Figures assume that
transit is always fully
occupied
Many transit riders
agree with this
Thus, it must be the
case that transit has a
higher load factor

But, many seem to be
committing a “fallacy
of composition”
Does Data Suggest Load Factor Fallacy?

Average Number of
Persons/Auto in SF

– 1.5

Average Number in
National Study
– 1.6 during rush hour
– 2.2 on the whole

So, nationwide auto
load factor: 25-30%
Rough estimates on
transit load factors:
– Bus: 18%
– Electric Transit: 26%

So, it would seem that
autos have a higher
load factor overall
What Accounts for Difference?

Buses and autos both

– Use pneumatic tires
– Run on an internal
combustion engine

– High pressure tires
(90 lbs/in2)
– More efficient diesel
engine
– Not overpowered, so
less acceleration
But,
– A bus may have a
higher weight per seat
than auto
– Aerodynamic drag not
a factor in city
Then, why are buses
more efficient?

Designing autos the
same way would
presumably have the
same effect
What About Rail?

Rail is inherently much more efficient
– Rolling resistance smaller than with tires
– Aerodynamic drag lower

One may calculate that rail is roughly twice
as efficient as either auto or bus
So Why Not Rail?


Advantages clearly
evident in freight
transport
These advantages do
not carry over to urban
transit

BART (SF Bay)
– Consumes as much
energy per mile as an
auto
– About half of this is
used for HVAC and
station lighting
– So, if one counts on
traction energy, rail
efficiency is roughly
equal to a bus
Why Is Rail So Inefficient?

High cruising speed
– Aerodynamic drag and
kinetic energy lost
when the train brakes
are both proportional to
square of the velocity

So, if one doubles the
train velocity, energy
losses become four
times greater


Aerodynamic drag
underground is also
significantly higher
than the surface
Many urban rail transit
systems are below
ground
American Public Transportation
Association: Mass Deceiver?
Much of this misinformation comes not
from environmentalists, but the APTA
 Recent reports released by APTA offer
untenable conclusions based on inconsistent
data

– Consider the data APTA offers on energy
consumption on auto and rail
APTA Conclusions

Miscalculation of Rail
Energy Consumption
– APTA underestimates
the amount of energy
used by rail by at least
25%
– Indeed, rail uses
approximately 4 times as
much energy as APTA
claims
– APTA ignores oil 
electricity production
and transmission losses

Miscalculation of Auto
Energy Consumption
– Overestimates the
amount of energy used
by trucks and SUVs by
about 1/3
– APTA includes
commercial vans in
calculations
– APTA overestimates
amount of energy saved
by switching from trucks
and SUVs by up to 10
times
APTA’s “European” Goal

APTA claims that if Americans used transit
as much as Europeans, they would require
40% less Persian Gulf oil
– To attain Europe’s 10% ridership, however,
would require a 900% increase in U.S. ridership
– But, the U.S. Census Bureau announced that
transit use is at a 40-year low.
APTA Hallucinations




People like transit
where it is competitive
with their autos
But auto-competitive
transit is available to
one place: downtown
Even then, it is only
available in large
urban areas
Of all commuters,
transit attracts:
– 75% to Manhattan
– 60% to Chicago Loop
– 30 to 50% in Brooklyn,
Boston, San Francisco,
Philadelphia,
Washington DC, and
Seattle

The APTA figures, then
would require (roughly)
a 750% increase in
ridership in Manhattan!
Towards Alternative Criterion of
Evaluation
If APTA’s statistical “facts” cannot be
indicted completely, it is clear that, at the
very least, the criterion for evaluating transit
need to be reconsidered
 We suggest moving the debate from
technological to social considerations

Alternative Considerations

Pleasant, hassle-free transit service
encourages people to live farther from work
– These longer trips waste more energy

Getting drivers out of autos and into transit
results in less highway congestion
– This, however, entices highway use even more

Perhaps the solution lies in auto use and
land-use restrictions
– Force people to live closer to work
Auto and Land-Use Restrictions

While autos require excessive space for
parking
– This, however, has helped limit high-density
development

By diverting traffic to mass transit, this
paves the way for high-density, central-city
development in the open spaces
– So, the advantages of transit become liabilities
in the absence of effective auto and land-use
controls
Other Questions

Multibillion-dollar transit subsidies raise
questions of equity and efficiency:
– Will these increase/decrease energy
consumption and pollution?
– Will they promote efficient operation?
– Will someone who does not use transit (walks,
rides bicycle instead) be required to pay taxes
on subsidies?
– Does subsidy encourage excessive wage
demands from transit employees?
Conclusions



We have been, and are currently using, petroleum
at an unsustainable rate
It appears that a change in energy consumption
cannot be achieved merely by changing
technology or modes of transit
The solution then is twofold:
– Responsible urban planning
– Institution of anti-mobility measures

The ultimate goal then, is a gradual paring down
of transportation demand
– Simply considering only efficient transit alternatives is
not rational problem-solving
References

Slides 2-4:
Statistics gathered from the American Public Transportation Association website.
http://www.apta.org
Stephanie Corson. “Private Transportation vs. Mass Transit: The Environmental
Aspects”. http://www.cas.usf.edu/philosophy/mass/Stephanie.html

Slides 5-10:
Lawyer, David S. “Transportation: Warnings on Mass Transit”. Environment, Vol.
17, No. 6.
Hirst, Eric. Oak Ridge National Laboratory Report, ORNL-NSF-EP-44.

Slides 11-18:
American Public Transit Association. “Conserving Energy and Preserving the
Environment: The Role of Public Transit.” http://www.apta.org
Cox, Wendell. “Mass Mythology: Transit Myths Disguised as Science,” National
Review, 7/24/02.
U.S. Census Bureau. Facts and analysis on mass transit ridership. U.S. Census
Bureau’s website.
Kbol, Ronald. “Attracting Consumers to Mass Transit,” Machine Design, Vol. 74,
Issue 18