AY REU Seminar

Nov. 9, 2012

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Heng Wei, Ph.D., P.E.Associate Professor, School of Advanced Structures

Creative Interdisciplinary Research Thinking: Example of Connecting Air Pollution and Public

Health Impact with Transportation

AY REU Seminar

Nov. 9, 2012

1. Problem Identification Ability 2. Solution Development Ability 3. Solution Evaluation Ability

Three Primary Ability

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Nov. 9, 2012

ScienceTechnologyEngineeringModeling/Math

System

Solution DevelopmentSTEMS Appraoch

AY REU Seminar

Nov. 9, 2012

Environmental Issues: Mobile Source EmissionSustainable Issue: meet the mobility needs of the present without compromising the ability of future generations to meet their needsPolicy issue: ......

Complex Transportation Problems

Integrated ATMS/ATIS

AY REU Seminar

Nov. 9, 2012 Transportation Sustainability Concern? Challenges in transportation environmental impact

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Nov. 9, 2012

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Traffic-Generated Air Pollutants

• The tailpipe emissions of vehicles, as a consequence of The incomplete burning of carbon in fuels such as gasoline or diesel produces, include: carbon monoxide (CO) particulate matter (PM) hydrocarbons (HC) nitrogen oxides (NOx) carbon dioxide (CO2) volatile organic compounds (VOC)

• Particulate Matter (PM2.5): a mixture of solid particles and liquid droplets found in the air.

• Transportation greenhouse gases (GHGs) emissions are primarily in the form of CO2, increase of which may prevent heat radiation/loss from the earth to the space and cause climate change.

• The highway vehicle emission is the main source for CO2. Heavy duty vehicles contribute to 23% of the on-road GHGs emissions, out of which 97% is related to freight haulage.

AY REU Seminar

Nov. 9, 2012

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Factors influencing human health

• Elevated levels of air pollutants (e.g., CO, PM, and NOx ) from traffic exhaust near major roadways are associated with adverse health effects in children, such as respiratory allergies, decreased lung function and development, bronchitis (支气管炎 ), and asthma (哮喘 ) exacerbation.

• Truck routes generally run along major roadways aerosolizing harmful particles (e.g., diesel exhausts PM). Diesel fuel powered school buses also represent a major exposure source.

• Proximity to the pollution source is a reliable estimate of exposure.

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Nov. 9, 2012

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(Compressed natural gas)

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Transportation Conformity

• Goal under the Clean Air Act: control and reduce adverse environmental impact of traffic-generated air pollution.

• Localized analysis of traffic‐generated pollutants (e.g., CO) is often required by the U.S. Environmental Protection Agency (EPA) to determine project‐level air conformity of transportation projects in accordance with State Implementation Plan (SIP).

AY REU Seminar

Nov. 9, 2012

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Air Quality Standards

An area is in violation of a standard if it exceeds the concentration level for its evaluation time frames. For example, for an area to attain the 8-hour ozone standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations measured at each monitor within the year must not exceed 0.08 ppm.

National Ambient Air Quality Standards (NAAQS) are set by EPA to protect public health and welfare. Primary standards are designed to protect against adverse health effects, while secondary standards protect against welfare effects, such as damage to crops, vegetation, buildings, and decreased visibility.

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Nov. 9, 2012

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• Emission Equivalence= emission factor × vehicle travel activity (speed, VMT) × other correction factors

• Total vehicle fuel consumption = vehicle travel activity × fuel intensity (e.g., litres/100km)

• Total vehicle emissions = Fuel consumption × emission equivalences

Traffic Emission Modeling

Emission factor approaches:

Approach 1: Generated from a vehicle emission model (MOBILE, MOVES, EMFAC)

Approach 2: Derived from a speed-emission curve, table or equation

Approach 3: Estimated from vehicle fuel consumptions

AY REU Seminar

Nov. 9, 2012

12FHWA vehicle speed-emission curve

Emission Factors: Speed-Emission Curve

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Nov. 9, 2012

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Emission Factors: Vehicle Fuel Consumption

Travel model outputs Fuel consumption GHG emissionsVMT/VKT, vehicle type, average speed by fuel type CO2, CH4, N2O

Speed-fuel consumption curve

Driving 55mph -- Is it the most efficient speed?

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Nov. 9, 2012

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How MOVES Handles Vehicle Activity?

• Vehicle Specific Power (VSP) – the instantaneous power per unit mass of the vehicle, which is generated by the engine to overcome the rolling resistance and aerodynamic drag, and to increase the kinetic and potential energies of the vehicle; a measure of the energy the vehicle is using at a moment in time

– Speed, acceleration, and road grade are key factors influencing fuel consumption for diesel and hydrogen fuel cell buses under real-world operating conditions. VSP is a proxy variable for engine load that has been shown to be highly correlated with emissions.

– Affected by acceleration, road grade, resistance, etc.• Operating Mode – what the vehicle is doing, i.e., accelerating,

braking, cruising, idling– Vehicles use different VSP in different operating modes

– MOVES defines 23 operating mode bins – combinations of speed and VSP for different running conditions plus additional operating modes for starts and evaporative emissions

• Drive Cycle – a second-by-second description of vehicle activity over time, typically including multiple operating modes

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Nov. 9, 2012

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Vehicle Specific Power (VSP)

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Nov. 9, 2012

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Vehicle Specific Power (VSP)

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Emission vs. VSP

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Emission vs. VSP

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Air Pollution Dispersion Modeling

• Air quality models are used to predict ground level concentrations down point of sources. The object of a model is to relate mathematically the effects of source emissions on ground level concentrations, and to establish that permissible levels are, or are not, being exceeded.

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Nov. 9, 2012

x-axis - Alongwind; y-axis - Crosswind; Parameters:C = Concentration (mg/m3)Q = Emission Rate (g/s)u = Stack-top wind speed (m/s)sy = Crosswind dispersion coefficient (m)

z-axis - Vertical

sz = Vertical dispersion coeff.(m)y = Crosswind distance (m)z = Above-ground height (m)H = Effective plume height (m)

Gaussian Dispersion Equation

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Ambient concentration is a function of emissions, downwind, lateral, and relative vertical distance from the source, cross-wise distance from the flow direction, wind speed, and PGT stability class.

AY REU Seminar

Nov. 9, 2012 Gaussian Plume

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AY REU Seminar

Nov. 9, 2012Gaussian Finite

Line Source Model

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Nov. 9, 2012 Intersection Model

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Connecting Traffic, air pollution and exposure risk to air pollutants

MOVES

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Nov. 9, 2012 School Students’ Exposure to Traffic Air Pollutants (Cincinnati Case)

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• Public school data were obtained from the US Department of Education’s National Center for Education Statistics (schools pre-kindergarten to grade 12).

• Statistical analysis– Difference in percentages of schools and students

within each Minority School Area (MSA) were tested using a z-test for differences in proportions.

Percent of proximal exposure at distances X = 100 m and X = 400 m was calculated as

MSA theof udentsschools/st ofnumber Total

Highway Stateor US,,Interstatean of meters X within udentsschools/st ofNumber PE =

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Nov. 9, 2012 PE Result (US Cities)

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Percent of schools/students nearan Interstate, US, or State highway ≤400 m ≤100 mSchools Students Schools Students

Boston, MA 43.9 44.4 18.5 18.9Philadelphia, PA 41.5 41.3 17.6 18.0Atlanta, GA 38.4 35.9 18.2 17.6Cincinnati, OH 38.5 38.1 18.3 19.0Memphis, TN 35.7 32.8 14.3 13.1Minneapolis, MN 38.1 35.7 10.9 9.7San Antonio, TX 25.2 22.0 6.8 7.3Denver, CO 26.3 23.1 7.6 5.2Los Ángeles, CA 19.5 20.5 3.2 3.5

Total (for 9 MSAs) 33.0 30.4 11.9 10.8

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Flo

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Planning Scenario Development

Corridor Scenario Development

Emission Analysis Tools

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VISUM (Macro)Area Analysis

VISSIM (Micro)Corridor Analysis

Defined Area Network in VISUM

Defined Corridor-Centered Network in VISSIM

Link-based Traffic Flow Features

Lane-Based Traffic Flow Features

Transportation Modeling Calibration & Validation

Roadway Air Impact Analysis (RAIA) System in SB-PSS

Traffic Management and/or Control

Alternatives

Planning Alternatives with Travel Demand Forecasting

GIS-Based Data: Land Use, Social Economic, Transportation Infrastructures (Base year

traffic used for model calibration & validation)

Transportation Modeling Calibration & Validation

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Input to SB-PSS Data Layer

Emission Factors using MOVES and Other Dispersion

Models

Roadway Link, or Corridor or Area Based Network Emission and Dispersion Levels

in GIS Platform

Evalu

ation of T

raffic Man

agemen

t Altern

ative

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Preliminary Case Research

Figure 7:

Taking advantage of existing traffic & air pollution monitoring data

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Sustainability Score as A Composite Indicator

1

q

j i iji

CI w X

Where: CIj is the composite index for each Traffic Analysis Zone j.

Xij is the normalized indicator (i=1,2,…,q, j=1,2,…,m)

wi is the weight of the indicator

Indicators Recommended by EPA*:

Carbon Intensity: Measures the amount of carbon dioxide (CO2) emitted from transportation per personLand Consumption: Measures the amount of land consumed by development areas which are accessible by traffic. The current algorithm uses the summation of area of land use class 1 to 8 divided by the total area of the TAZMixed Land Use: Measures the proportion of residents living in locations with mixed land uses.Transit Accessibility: Measures the ability of people to reach destinations using public transportation. The average distance from transit stops to TAZ centroids were calculated by using their spatial relationship.VMT per Capita: Measures the amount of vehicle activity normalized by population

* US EPA “Guide to Sustainable Transportation Performance Measures” (2011)

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Sustainability Assessment (2020)

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Scenario Development

• Travel trips are forecasted based on the settings of land use, social economic data and transportation infrastructures.

• Vehicle miles traveled on automobiles and trucks as well as speed profiles are resulted from the forecasting models.

• Resulted transportation activities as inputs to MOVES.

VISUM Difference Network Showing Traffic Impacts on Base and Scenario Model (Red line shows increased traffic volume and green shows reduced traffic volume)

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Integration of Regional and Project Levels(Field Data Collection for Emission Simulation Modeling Validation)

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Traffic Operation and Emission Measurement

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UC Campus Case Study

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Question?

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