APPENDIX A4 - Ground Access Vehicles Emissions  Inventory for Criteria Pollutants  A4.1  Overview  A4.2  Methodology  A4.2.1  On- and Off-Airport Roadways  16  Ground access vehicles exclude those ground support equipment (GSE) used for servicing aircraft and airports.  Equation A4-1. Total Pollutant Emissions from Traveling Motor Vehicles  Where:  E$_{Travel }$ = total traveling motor vehicle emissions of a pollutant (i.e., CO, SO$_{2}$, PM$_{10}$, PM$_{2.5}$, NO$_{x}$,  or VOC), for a given time period, expressed in pounds.  CF = factor to convert grams to pounds (i.e., 0.0022046)  VMT$_{j }$= vehicle-miles-travelled on a roadway segment by vehicle type j (e.g., Honda Civic) for a  given time period, expressed in miles.  ER$_{j }$ = emissions rate of pollutant considering speed and vehicle type j, expressed in grams of  pollutant per mile.  j = vehicle type (e.g., Honda Civic).  𝑬 𝑳𝑻𝑻𝑻𝑻𝑻 =  𝑪𝑭 ×  ෍ൣ𝑽𝑻𝑳 𝒊 ×  𝑬𝑬 𝒊 ൧ 𝒊 Emissions from motor vehicles traveling on- and off-airport roadways are primarily a function of  vehicle-miles-travelled (VMT) within a specific roadway segment by a specific type of vehicle  (e.g., passenger cars, diesel shuttles, compressed natural gas [CNG] buses, etc .). VMT are then  factored against a series of pollutant emissions rates for that type of vehicle, in grams per VMT,  to compute emissions. This approach is also employed for the component of parking curbside activities associated with vehicle travel (as opposed to vehicle idling). Emissions from  ground access vehicles traveling on- and off-airport roadways may be estimated by applying  Equation A4-1  ( Total Pollutant Emissions from Traveling Motor Vehicles ).  Ground access vehicle emissions are typically associated with three different types of airport  activities: (i) vehicles traveling on- and off-airport roadways, (ii) vehicles traveling and idling  within airport parking facilities; and (iii) vehicles accessing and idling at terminal curbside areas  associated with passenger pickup and drop-off.  Ground access vehicles 16  include airport passenger vehicles (e.g., private autos, taxis, limousines,  shuttles, vans, buses, rental cars, etc.), vehicles transporting airport and tenant employees, airport  fleet (e.g., buses, shuttles, etc.), and vehicles transporting cargo to and from the airport as well as  circulating around the airport. This appendix details the methodology for computing emissions  from ground access vehicles associated with airport activities.  APPENDIX A4$_{ }$ 18$_{ }$