Click for next page ( 77


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 76
APPENDIX Transit Air Benefits Calculator: Description and User's Manual Air Pollutants To conduct a simple evaluation, one often looks at the "criteria pollutants." These pollutants-- defined by the Clean Air Act--include oxides of nitrogen (NOx), sulfur dioxide (SO2), carbon monoxide (CO), ground-level ozone (O3), particulate matter (PM), and lead. Following is a description of the criteria pollutants and other significant pollutants. Oxides of Nitrogen NOx cause respiratory problems and contribute to ozone formation, acid rain formation, nutrient overloading of lakes and streams, regional atmospheric haze, and global warming. Ozone Ozone is primarily formed through a chemical reaction involving sunlight, NOx, and volatile organic compounds (VOCs). Motor vehicles are the largest source of NOx and the second largest source of VOCs, accounting for 36% of all NOx and 22% of all VOCs emitted nationally.1 Ozone is linked to a variety of respiratory problems including lung irritation, wheezing, coughing, dif- ficulty breathing, aggravated asthma, and reduced lung capacity. Particulate Matter PM is a term referring to small, respirable particles in solid and liquid form. PM can be com- posed of any number of materials including dust, organics, metals, and acids. Smaller, fine par- ticles are more toxic than larger ones because they can be inhaled deeper in the lungs and absorbed in the bloodstream instead of being exhaled. Buses emit a greater portion of smaller or fine particles than do motor vehicles. About 50% of PM from cars is considered fine (i.e., less than or equal to 2.5 micrometers, or "PM2.5"); about 90% of diesel particulate (from buses) is fine.2 Highway vehicles3 generate about 1% to 3% of all particulate matter. 1 Source: U.S. EPA data for 2006, www.epa.gov/ttn/chief/trends/trends06/nationaltier1upto2006basedon2002finalv2.1.xls as of October 2007. 2 Based on National Mobile Inventory Model (NMIM) output for Burlington, VT, 2008 model run. 3 Source: U.S. EPA data for 2006, www.epa.gov/ttn/chief/trends/trends06/nationaltier1upto2006basedon2002finalv2.1.xls as of October 2007. 76

OCR for page 76
Appendix 77 Oxides of Sulfur SO2 is generated primarily by electric utilities. With fuel sulfur standards dropping to 15 ppm, very little is generated by highway vehicles (about 1%).4 SOx compounds contribute to acid depo- sition, create atmospheric haze, and can cause respiratory illness, especially in children and the elderly. Carbon Monoxide CO has many side effects because it displaces oxygen in the bloodstream. As a result, it can cause dizziness, affect the central nervous system, affect people with heart disease, and contribute to smog. Oxidation catalysts have reduced highway vehicle CO emissions by 66% since 1970 despite the large increase in VMT over that time period.5 As a result, only three cities in the United States are in non-attainment for CO. Lead Lead damages the kidneys, liver, brain, and nervous system; causes heart disease; and can last a long time in the environment. Lead was a serious concern when the 1970 Clean Air Act was established. Consequently, a phase-out of lead in gasoline was initiated. Since that time, overall lead emissions from motor vehicles have been virtually eliminated. Air Toxics/Hazardous Air Pollutants There is another category of pollutants called "air toxics," also referred to by the U.S. EPA as hazardous air pollutants (HAPs). These are known to or suspected in causing cancer or other serious health effects such as birth defects, respiratory disease, immune system defects, neuro- logical problems, and other problems through chronic and/or acute exposure. There are no fed- eral limits to air toxics concentrations in ambient air; however, many states have adopted their own standards. According to the U.S. EPA, motor vehicle air toxics are expected to decline by 75% between 1990 and 2020 due to the introduction of reformulated gasoline and tailpipe emis- sion limits. Greenhouse Gases Greenhouse gases are a separate category of pollutants that contribute to global warming. Com- monly known greenhouse gases are water vapor, carbon dioxide, tropospheric ozone, nitrous oxide, and methane. Motor vehicles directly emit or contribute to the creation of each of these greenhouse gases. Water vapor and carbon dioxide emissions are a function of vehicle fuel effi- ciency, while nitrous oxide and methane are functions of both fuel efficiency and combustion method (e.g., diesel or spark ignition). For example, buses have seven times the carbon dioxide emissions of cars/light trucks6, but about 10% of the nitrous oxide and 3% of the methane emis- sions per mile.7 4 Source: U.S. EPA data for 2006, www.epa.gov/ttn/chief/trends/trends06/nationaltier1upto2006basedon2002finalv2.1.xls as of October 2007. 5 Source: U.S. EPA data for 2006, www.epa.gov/ttn/chief/trends/trends06/nationaltier1upto2006basedon2002finalv2.1.xls as of October 2007. 6 2008 NMIM model runs for Burlington, VT. 7 "Update of Methane and Nitrous Oxide Emission Factors for On-Highway Vehicles," U.S. EPA, EPA420-P-04-016, Novem- ber 2004.

OCR for page 76
78 Planning for Offsite Airport Terminals State Implementation Plans As noted previously, VOCs and NOx are ozone precursors and also contribute to atmospheric haze. While there are National Ambient Air Quality Standards (NAAQS) that limit concentra- tions of criteria pollutants in ambient air, there are also often limits established for NOx and VOC emissions in certain regions due to non-attainment of ozone standard(s). These limits are set in State Implementation Plans (SIPs). SIPs are regulations, adopted by a state and approved by the EPA, that establish a plan to meet requirements of the Clean Air Act. In particular, for large metropolitan areas, SIPs may contain emissions budgets, transportation conformity requirements, and limits on industrial sources. "Transportation conformity" refers to a set of rules that requires the transportation system and transportation plans to meet the requirements of the SIP. Transit systems and bus retrofits are often part of a region's transportation plan and are used to meet emissions reduction budgets specified in SIPs. Emissions reductions that are credited must be quantified using methods and models approved by the U.S. EPA. Transit Air Benefits Calculator The Transit Air Benefits Calculator, a spreadsheet program, was developed by the project team to estimate the change in various air pollutants and overall air pollution resulting from the air- port transportation link serving an offsite airport terminal. It calculates emissions of 40 pollu- tants from cars, pickup trucks, SUVs, and buses for 24 cities between the years 2006 and 2028. It also aggregates pollutants to assess the net change in overall non-cancer health risk and green- house gas emissions. When first started, an opening screen is displayed (see Figure A-1). This shows the user the project name and the funding source. On the initial screen, the user clicks on the start button to move to the main calculations page. Figure A-1. Transit benefits calculator start page.

OCR for page 76
Appendix 79 The Main calculations sheet has portions which accept user inputs (shaded in gray) and the results (Figure A-2). The process for running a scenario is as follows: 1. Select an analysis year--the user can select 2006, 2007, or any other even year from 2008 to 2028. The analysis year is used to take into account reductions in emissions due to retirement of older, dirtier vehicles in the fleet. 2. Select the nearest city--the calculations of bus and car/light truck emissions are based on runs from the U.S. EPA's National Mobile Inventory Model (NMIM), which, in turn is based on the U.S. EPA's Mobile6.2 motor-vehicle emissions model. Different cities and counties have different emission rates due in part to Temperature and humidity, Gasoline formulation and vapor pressure, Inspection/maintenance programs, Anti-tampering programs, and Fleet-vehicle-type mix. The Calculator considers each of these different factors for each city and computes valid motor vehicle emission rates specific to the county in which the city is located. At present, Source: Resource Systems Group, Transit Air Benefits Calculator. Figure A-2. Transit Air Benefits Calculator: main calculations page.

OCR for page 76
80 Planning for Offsite Airport Terminals Source: Resource Systems Group, Transit Air Benefits Calculator. Figure A-3. Simplified displaced passenger VMT calculator. 24 cities in 23 states are represented in the calculator. Note that two cities in the Calculator are in California. NMIM is not approved for use in calculating authorized SIP reductions in California; therefore, results for California should be viewed with caution. California uses the EMFAC model,8 which is specific to that state. 3. Enter displaced passenger vehicle VMT--the VMT for passenger vehicles displaced by the airport transportation link is entered in Cell E11. This VMT may be for an hour, week, month, or year so long as the user uses a consistent unit throughout the worksheet. We recommend the use of annual VMT since emissions are based on the average of January and July Mobile6.2 emission rates. The VMT savings should be calculated using the methodology described in Chapter 6 of this report, taking into account all low-occupancy-vehicle modes including taxi, limousine, private automobile pick-up/drop-off, and private automobile long-term parking. However, if the data is not available for calculating VMT savings at this level of detail, the Transit Air Benefits Calculator includes a simplified VMT calculator method that simply con- siders the number of buses per day, average number of passengers per bus, the automobile occupancy of the displaced passenger cars, the number of round trips per bus, and the round trip miles per bus (Figure A-3). To access the calculator click on the calculator button to the right of the VMT entry cell (Cell E11). The Total Daily VMT would be equal to (Average Passengers per Bus) (Number of Buses per Day) (Automobile Occupancy) (Round Trips per Bus) (Miles per Round Trip). The Weekly VMT is calculated as follows: (Weekday VMT) 5 + (Weekend VMT) 2. The Annual VMT is as follows: (Weekly VMT) 52. 8 www.arb.ca.gov/msei/onroad/latest_version.htm as of October 2007.

OCR for page 76
Appendix 81 Table A-1. Types of transit vehicles and emissions in the calculator.* Type of Transit Vehicle NOx PM HC** CO CO2 Conventional Diesel (15 ppm Sulfur) 0% 0% 0% 0% 0% Biodiesel B2 1% 2% 1% 0% Biodiesel B10 2% 4% 11% 5% 1% Biodiesel B20 4% 10% 12% 10% 1% Biodiesel B100 10% 37% 69% 40% 5% Compressed Natural Gas 50% 95% 50% Emulsion 15% 20% Source: U.S. EPA Diesel Emission Quantifier. *Values shown indicate the percentage reductions in emissions relative to conventional diesel. Negative values indicate increases in emissions relative to diesel. Missing values are not known and treated as 0%. **HC = hydrocarbons. Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-4. Instructions and list of fuel types. Passenger vehicle emissions are based on emissions from passenger cars and light-duty gaso- line trucks, weighted by the actual VMT mix for the chosen city. 4. Enter the transit service parameters--the block of cells in grey under Transit Service Parame- ters allows the user to input up to four different types of vehicles in the bus fleet. For example, if the fleet were made up of 75% conventional buses and 25% compressed-natural-gas (CNG) buses, these two would be entered in separate rows with the VMT allocated proportionally. a. Enter the type of buses in the fleet--the bus choices available and the associated emissions reductions are based on the U.S. EPA's Diesel Emission Quantifier.9 The quantifier is an online calculator for estimating the reduction in a fleet of diesel equipment. The quantifier should not be used to calculate emissions reductions to be incorporated into a SIP without first consulting the U.S. EPA Regional Office and SIP guidance documents. The types of transit vehicles modeled are shown in Table A-1. The numbers after "Biodiesel" indicate the percentage of biodiesel in the fuel--for example, B20 is 20% biodiesel and 80% con- ventional diesel. The list can be accessed by clicking on the cell, then clicking on the arrow to the right of the cell (see Figure A-4). Instructions automatically appear when the cell is 9 cfpub.epa.gov/quantifier/view/index.cfm as of October 2007.

OCR for page 76
82 Planning for Offsite Airport Terminals Table A-2. Emission-control technologies with emissions reductions in the calculator. Emission Control Technology NOx PM HC CO CO2 Diesel Oxidation Catalyst 20% 50% 30% Diesel Oxidation Catalyst + Closed Crankcase Ventilation 25% 40% 30% Diesel Particulate Filter 85% 90% 90% Diesel Particulate Filter + Closed Crankcase Ventilation 95% 90% 90% Diesel Particulate Filter + Lean NOx Catalyst 25% 90% 75% 75% Diesel Particulate Filter + Hybrid Electric 50% 95% 90% Diesel Particulate Filter + Exhaust Gas Recirculation 40% 90% 90% 90% Partial Flow Filter 50% 75% 75% Recalibration 25% Selective Catalytic Reduction 70% 40% 70% 90% Source: U.S. EPA Diesel Emission Quantifier clicked (left); the list of fuel types are shown for a given selection when the drop-down arrow to the right of the cell is clicked. b. Enter the emissions control technology for the bus--as above, the emission-control tech- nologies are those found in the U.S. EPA's Diesel Emissions Quantifier. The list with their associated emissions reductions is shown in Table A-2. When the grayed cell is clicked, instructions pop up, and when the arrow to the right is clicked, the list of emission controls to select pops up (see Figure A-5). Emission-control technologies instructions appear when the cell is clicked (left); the list of emission controls are shown for selection when the drop- down arrow to the right of the cell is clicked (right). c. Enter the idling-control strategy for the bus--as above, the idling strategies are those found in the U.S. EPA's Diesel Emissions Quantifier. The list with their associated emis- sions reductions are shown in Table A-3. If no control strategies are used, the cell can be left blank. The cell instructions and drop-down list are shown in Figure A-6. Idle Control Strategies instructions appear when the cell is clicked (left); the list of strategies is shown for a selection when the drop-down arrow to the right of the cell is clicked (right). d. Enter the VMT for the bus type--enter the VMT of the particular bus type into Column F (see Figure A-7 for instructions). A simplified method for calculating the VMT is available Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-5. Instructions and emission-control technologies.

OCR for page 76
Appendix 83 Table A-3. Idle-control strategies with emissions reductions in the calculator. Idling-control Strategies NOx PM HC CO CO2 Direct-fired Heater 98% 99% 95% Auxiliary Power Unit 94% 81% 73% Engine Shutdown 100% 100% 100% Plug-in 95% 100% 100% Source: U.S. EPA Diesel Emission Quantifier Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-6. Instructions and idle-control strategies. by clicking on the calculator button to the right of the word "VMT." The calculator, shown in Figure A-8, calculates Annual VMT as follows: Daily VMT = (Number of Buses per Day) (Average Number of Round Trips per Bus) (Miles per Round Trip); Weekly VMT = (Weekday VMT) 5 + (Weekend VMT) 2; and Annual VMT = (Weekly VMT) 52. The Bus VMT Calculator estimates annual VMT based on buses per day, round trips per bus, and miles per round trip. e. Enter the idling time for the bus type--the idling time of the particular bus types should be entered in Column F (see Figure A-9 for instructions). However, a simpli- fied method is also available by clicking on the calculator button in the column header. The calculator, shown in Figure A-10, calculates idle time as follows: (Number of Buses per Day) (Number of Round Trips per Bus) (Stops per Round Trip per Bus) (Minutes per Stop) + (Minutes of Idle during Warm-up and Shutdown) Daily Idle Time in Hours = (60 minutes/hour); rs = (Weekday Idle) 5 + (Weekend Idle) 2; and Weekly Idle Hour Annual Idle Hours = (Weekly Idle) 52. The idle-time calculator estimates annual idling hours based on the buses per day, round trips per bus, number of stops, idle time per stop, and idling at the garage.

OCR for page 76
84 Planning for Offsite Airport Terminals Source: Resource Systems Group, Transit Air Benefits Calculator Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-8. The VMT calculator. Figure A-7. On-screen instructions for entering bus VMT. As inputs are entered, the results are automatically calculated. A screenshot of the results is shown in Figure A-11. The first two rows of the table show the total bus-operating and bus-idle emissions in tons for NOx, PM10, VOC, CO, and CO2, with the third row showing the sum of the first two rows. The next row shows the tons of these pollutants reduced from the displaced passenger vehicles (cars, pickups, and SUVs). These emissions are based on runs of the U.S. EPA's NMIM model and are based on all roadway types and a default mix of vehicle speeds. Note that emissions improvements due to reduced levels of congestion resulting from diversions to the transit mode aren't taken into account. This can be calculated using other models, but is likely a secondary effect with less impact on emissions than from VMT reductions. The net change in emissions is shown next. A negative value indicates a reduction in regional emissions and, thus, a net improvement in air quality for that pollutant. Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-9. On-screen Source: Resource Systems Group, Transit Air Benefits Calculator instructions for entering bus-idling time. Figure A-10. Idle-time calculator.

OCR for page 76
Appendix 85 Net Change in Emissions Back to Main NOx PM10 VOC CO CO2 Bus running emissions 44.0 0.4 0.4 3.1 7252.8 tons Bus idling emissions 0.1 0.0 0.0 0.0 20.6 tons TOTAL Bus Emissions 44.1 0.4 0.4 3.1 7273.4 tons minus Passenger Vehicle Emissions Offset 57.4 1.4 65.2 928.5 21399.2 tons Net Change in Emissions -13.3 -1 -64.8 -925.4 -14125.8 tons Net change in greenhouse gas emissions equivalent to CO2 emitted by -1,443,587 gallons of gasoline per year Note: A negative change indicates a net reduction in air emissions. Source: Resource Systems Group, Transit Air Benefits Calculator Figure A-11. Main results table in the calculator. At the present time, the calculator only estimates one greenhouse gas--CO2. The total gaso- line equivalent shown in Figure A-11 is equal to the net change in CO2 multiplied by 102.195 gal- lons of gasoline combusted per ton of CO2 emitted. NMIM calculates emissions for a total of 39 pollutants including criteria pollutants, HAPs, and greenhouse gases. The change in emissions of all these pollutants is shown in the "Results" tab of the workbook. The output for the sample problem shown above is illustrated in Table A-4. Outside of the calculator, the user can use the results and weight the emissions of each pollu- tant to create a single non-cancer and cancer health impact score. There are several weighting schemes available.10 10For weighting schemes, see "Human Toxicity Potentials for Life-Cycle Assessment and Toxics Release Inventory Risk Screen- ing" in Environmental Toxicology and Chemistry by E.G. Hertwich, S.F. Mateles, W.S. Pease, and T.E McKone; SETAC 2001; 20(4): 92839.

OCR for page 76
86 Planning for Offsite Airport Terminals Table A-4. Change in running emissions for all pollutants calculated by NMIM. Net change in running emissions for all pollutants Passenger Bus Running Vehicle Net Change Emissions Offset in Emissions Pollutant (tons) (tons) (tons) Ethyl benzene 1.12E-02 1.45E-03 9.78E-03 Styrene 1.95E-03 1.52E-03 4.29E-04 1,3 Butadiene 2.87E-03 4.65E-03 -1.78E-03 Acrolein 3.19E-04 2.67E-03 -2.35E-03 Toluene 7.46E-02 2.32E-03 7.23E-02 Hexane 1.25E-02 3.99E-03 8.52E-03 Anthracene 2.78E-06 2.53E-05 -2.26E-05 Propionaldehyde 3.44E-04 4.42E-03 -4.08E-03 Pyrene 4.08E-06 2.67E-05 -2.26E-05 Xylene 4.17E-02 3.48E-03 3.82E-02 Chromium6 1.46E-06 5.28E-07 9.33E-07 Benzo(g,h,i)perylene 8.41E-07 6.16E-06 -5.32E-06 Indeno(1,2,3,c,d)pyrene 2.52E-07 6.85E-07 -4.33E-07 Benzo(b)fluoranthene 4.00E-07 7.53E-06 -7.13E-06 Fluoranthene 2.99E-06 1.51E-05 -1.21E-05 Benzo(k)fluoranthene 4.00E-07 7.53E-06 -7.13E-06 Acenaphthylene 1.35E-05 2.53E-05 -1.18E-05 Chrysene 3.36E-07 4.79E-06 -4.46E-06 Formaldehyde 5.56E-03 5.96E-02 -5.40E-02 Benzo(a)pyrene 3.36E-07 8.90E-06 -8.57E-06 Dibenzo(a,h)anthracene 0.00E+00 0.00E+00 0.00E+00 2,2,4-Trimehtylpentane 2.61E-02 4.78E-04 2.57E-02 Benz(a)anthracene 3.36E-07 2.74E-05 -2.71E-05 Benzene 2.63E-02 8.00E-03 1.83E-02 Manganese 1.23E-06 8.23E-07 4.02E-07 Nickel 2.66E-06 2.64E-06 1.67E-08 Chromium(Cr3+) 2.19E-06 7.91E-07 1.40E-06 Acetaldehyde 2.10E-03 2.19E-02 -1.98E-02 Acenaphthene 2.40E-06 1.64E-05 -1.40E-05 Phenanthrene 8.33E-06 3.83E-05 -3.00E-05 Fluorene 4.96E-06 3.36E-05 -2.86E-05 Naphthalene 4.43E-04 9.59E-04 -5.17E-04 CO 11.887 3.606 8.281 CO2 273.969 1914.908 -1640.939 Nox 0.735 12.254 -11.519 PM10 0.019 0.769 -0.750 PM2.5 0.009 0.694 -0.686 SO2 0.005 0.200 -0.195 VOC 0.835 0.725 0.110 Note: A negative change indicates a net reduction in air emissions.