ENERGY AND ENVIRONMENTAL IMPACTS OF ROUTE CHOICE DECISIONS Kyoungho Ahn and Hesham Rakha Virginia Te

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ENERGY AND ENVIRONMENTAL IMPACTS OF ROUTE CHOICE
DECISIONS Kyoungho Ahn and Hesham
RakhaVirginia Tech Transportation Institute,
VPISU, Blacksburg, VA

• 1. Abstract
• The paper investigates the impact of route choice
  decisions on vehicle energy consumption and
  emissions using fuel consumption and emission
  models with second-by-second floating-car GPS
  data. The study investigates two routes a faster
  and longer highway route and a slower and shorter
  arterial route. The study demonstrates that the
  faster highway route choice is not always the
  best route from an environmental and energy
  consumption perspective. Specifically, the study
  demonstrates that significant improvements
  (savings of up to 63, 71, 45, and 20 percent in
  HC, CO, NOx, and CO2 emissions, respectively) to
  air quality can be achieved when motorists
  utilize a slower arterial route although they
  incur an additional 17 percent in travel time.
  Moreover, the study demonstrates that energy
  savings in the range of 23 percent can be
  achieved by traveling on the slower arterial
  route. The study also demonstrates that a small
  portion of the entire trip that involves high
  engine-load conditions has significant impacts on
  the total emissions, demonstrating that by
  minimizing high-emitting driving behavior air
  quality can be significantly improved.

• 3. Data Collection

4. Study Results

• 4.3 Case Study with Same Travel Time
• Emissions and fuel consumptions with same travel
  time

3.1 Study Corridor A morning commute GPS data
were collected in the Northern Virginia area. The
arterial route, VA Route 7, extends over 22.6 km
(17.25 mi) and covers 32 signalized intersections
while the highway route (35.85 km or 22.41 mi)
connects two highway sections and two arterial
sections with 8 signalized intersections. The
study corridors are controlled by a signal system
with an optimized cycle length of 180 seconds or
210 seconds depending on the time-of-the-day.
Most of the signal cycle time is assigned to the
main route, VA 7 and VA 28. The study utilizes
GPS data collected under current traffic signal
operations on the study sections during the
morning commute period.

• 4.1 Energy and Emission Models
• In order to estimate emission and fuel
  consumption using the second-by-second GPS probe
  vehicle data, the VT-Micro model, the
  Comprehensive Modal Emissions Model (CMEM), and
  the Environmental Protection Agencys (EPA)
  MOBILE6 model were utilized.
• 4.2 GPS Data Analysis
• Estimated emissions and fuel consumptions on
  study corridors.

2. Introduction Motorists typically choose routes
that minimize their travel time. Drivers may
select longer routes if they produce savings in
travel time. However, the question that needs
addressing is whether taking a longer but faster
route can result in energy and air quality
improvements. This study investigates the impact
of different route choices on vehicle fuel
consumption and emission rates using GPS data
gathered during the morning commute near a suburb
of the Washington, DC metropolitan area. The
objective of this study is to investigate the
impact of two route choices on vehicle fuel
consumption and emission rates. A number of
research efforts have attempted to develop
traffic assignment models that can enhance the
environment. However, these research efforts have
utilized simplified mathematical expressions to
compute fuel and emission rates based on average
link speeds without regarding transient changes
in a vehicles speed and acceleration levels. To
overcome the limitations of current research
methods, this study adopted microscopic fuel
consumption and emission models using
instantaneous speed and acceleration levels.
3.2 GPS Data Collection A portable GPS unit,
GD30L, manufactured by LAIPAC Technology Inc. was
utilized in the study. The GPS unit is designed
to record the date, time, vehicle longitude,
vehicle latitude, vehicle speed, vehicle heading,
and the number of tracking satellites. The GPS
floating-car travel data were collected on
weekdays (Monday through Friday) between March
and May of 2006 using a test vehicle. The trip
route (highway or arterial) was randomly selected
on the day of data collection. In order to record
the aggregate characteristics of traffic flow,
the probe vehicle maintained the average speed of
the traffic stream.
5. Conclusions
arterial route. Moreover, the study found that 23
percent of energy cost can be saved when
motorists sacrifice 17 percent of travel time by
traveling on the arterial route. Finally, the
study demonstrated that a small portion of the
entire trip (10 percent) that involves operation
at high engine loads can produce up to 50 percent
of the total trip emissions and consume up to 25
percent of the total trip fuel consumption.
Consequently, significant improvements in air
quality and energy consumption are achievable by
educating drivers.
This study demonstrates that a UE or SO traffic
assignment does not necessarily minimize vehicle
fuel consumption and emissions based on
second-by-second GPS commute field data. The
study demonstrates that, for the specific example
illustration, motorists could save 17 percent in
travel time on highway travel over travel on an
arterial route. However, significant improvements
(savings up to 63, 71, 45, and 20 percent of
emissions for HC, CO, NOX, and CO2, respectively)
to air quality are observed when motorists
utilize the slower