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Development of a Methodology for Estimating Vehicle Emissions

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... improve air quality. Automobile Pollution. Refuelling Emissions ... If the engine has been turned off for more than an hour, the trip is defined as 'cold' start ... – PowerPoint PPT presentation

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Title: Development of a Methodology for Estimating Vehicle Emissions


1
Development of a Methodology for Estimating
Vehicle Emissions
  • Jennifer Armstrong
  • Carleton University
  • August, 2000

2
Presentation Overview
  • Background
  • Research description
  • Input data preparation
  • Development of tools
  • Sensitivity analysis
  • Vehicle emissions in the NCR
  • Conclusions

3
Why Model Vehicle Emissions?
  • Analyze the environmental impacts of
    transportation and land use policies
  • use of high-occupancy vehicle lanes
  • major road network modifications
  • changes in transit ridership
  • Evaluate methods to improve air quality

4
Automobile Pollution
Refuelling Emissions
CO2 Estimated based on fuel consumption
Two Processes Combustion (Exhaust
System) Evaporation (Fuel Storage and Delivery
System)
5
Vehicle Emission Modelling
  • Criteria pollutants
  • Estimated using MOBILE5, an empirical model
    developed by the U.S. EPA
  • Emissions Base Emission Rate Adjustment
    Factors VKT
  • Greenhouse gas emissions
  • Estimated based on fuel sales or assumptions of
    average vehicle fuel efficiency
  • Emissions GHG emission factor fuel
    consumption rate VKT

6
Input Requirements
  • Emission models often require as input
  • number of vehicle kilometers travelled
  • average operating speed
  • trip length distribution

7
Travel Demand Models
  • Used to predict future traffic levels based on a
    regions demographic and socio-economic
    characteristics
  • Regional EMME/2 model can predict
  • number of vehicles per road segment
  • average operating speed
  • trip length distribution

8
Deficiencies of Current Practice
  • Assumption of average driver behaviour and trip
    characteristics may not be universally valid
  • Speed estimates from travel demand models may not
    be accurate
  • Model inputs are often based on default values,
    not local conditions

9
Model Integration
Emission Models
Travel Demand Models
MOBILE5
EMME/2
10
Model Integration
Emission Models
Travel Demand Models
MOBILE5
EMME/2
11
Research Methodology
  • PREPARE INPUT DATA
  • Intra-zonal travel
  • Operating mode characteristics
  • Commercial vehicle travel
  • Vehicle age distribution
  • Temperature data
  • COMPUTE VEHICLE EMISSIONS
  • Sensitivity tests
  • Vehicle age distribution
  • Operating mode fractions
  • Temperature
  • Trip length distribution
  • Speed
  • Vehicle mix
  • GHG emission fractor
  • Vehicle emissions in the NCR
  • DEVELOP TOOLS
  • EMME/2 macros
  • (summarize travel data)
  • The Emission Calculator
  • (computes vehicle emissions)

12
Study Area
Ottawa-Hull CMA Population 1 million
people Employment 500,000 jobs Land Area 5700
sq-km
13
Analysis Periods
  • Selected 5 analysis periods with similar travel
    characteristics

14
Road Classification Scheme
  • Developed a classification scheme based on
  • road capacity
  • local roads / centroid connectors
  • major and minor arterial/collectors
  • freeways and rural highways
  • transit-only roads
  • location within the study area
  • core, urban, suburban, rural

15
Intra-zonal Travel
  • Trips which begin and end in the same traffic
    zone are not assigned to the transportation
    network in EMME/2
  • To estimate the amount of travel associated with
    intra-zonal trips, TransCAD GIS was used to
    compute the shortest path between trip origins
    and destinations

16
Intra-zonal Travel - Analysis
17
Intra-zonal Travel - Results
18
Background Traffic
  • It is important to know the total volume of
    traffic using the transportation network
  • improve travel time estimates
  • improve vehicle emission estimates
  • EMME/2 only predicts passenger vehicle travel

19
Background Traffic
  • Analyzed data from the 1996 CO counts to
    determine the amount of commercial vehicle travel
  • Established vehicle mix ratios for freeways, and
    for arterial/collector roads in urban, suburban,
    and rural areas
  • Made assumptions regarding vehicle weight
    categories and fuel types

20
Background Traffic - Results
21
Operating Mode Analysis
  • Three operating modes
  • hot start
  • cold start
  • hot stabilized
  • If the engine has been turned off for more than
    an hour, the trip is defined as cold start

22
Operating Mode - Results
23
Operating Mode - Results
24
Temperature Inputs
  • Correspond to a typical October day
  • Based on temperature data measured at the Ottawa
    Intl Airport

25
Vehicle Age Distribution
26
EMME/2 Macros
  • Create an output file which summarizes travel
    data (vkt, link speed, trip length distribution,
    ...)

27
The Emission Calculator
  • Computes CO, NOX, and HC emissions using MOBILE5

28
The Emission Calculator
  • Computes greenhouse gas emissions using fuel
    consumption equations specified by the user

29
The Emission Calculator
30
The Emission Calculator
31
The Emission Calculator
32
Daily Vehicle Emissions
33
Daily Vehicle Emissions
34
Vehicle Emissions in the NCR
35
Vehicle Emissions in the NCR
36
Vehicle Emissions in the NCR
37
VOC Emissions
PM Peak Hour
38
NOX Emissions
PM Peak Hour
39
Benefits of Research
  • Development of tools to compute vehicle emissions
  • Estimation of vehicle emissions in NCR
  • Sensitivity analysis of input parameters
  • Illustration of a potential application of GIS in
    transportation planning
  • Analysis of intra-zonal trips, commercial vehicle
    traffic, operating mode fractions

40
Research Limitations
  • Ignored seasonal variation in emissions
  • Missing or incomplete data
  • vehicles with catalytic converters
  • linked trips
  • external trips
  • vehicle age distribution
  • fuel consumption equations
  • Estimation of 2021 emissions ignored changes in
    vehicle technology
  • Lack of speed post-processing

41
Recommendations
  • Consider seasonal variation in emissions
  • Update Emission Calculator for use with MOBILE6
  • Compare MOBILE5 and MOBILE6 results
  • Develop speed post-processors
  • Revise fuel consumption equations
  • Expand questions in OD Survey
  • Consider the impact of future technology
  • Comparison / validation of results
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