models is restricted by lack of appropriate traffic count and speed


The emission inventory guidance document13 provides direction

for developing mobile-source inputs from original data (referred to

as a bottom/up method) or from an existing county-level inventory

(referred to as a top/down method).


Bottom/up methods are the preferred approach for estimating

vehicle activity levels and emission factors because these

methods have potential for resolving variations in speed and

vehicle miles traveled (VMT) among different grids over hourly

time slices. Bottom/up approaches are most appropriate for

addressing the inner urban core of modeling domains.

Peripheral, less dense traffic areas can be treated with

top/down methods. Exceptions to these recommendations should

be considered by the Technical Committee on a case-by-case

basis. Justification for more extensive use of top/down

methods should be sought in discussions with the appropriate

EPA Regional Office.




n1151 n1152 - n1153 - n1154 - n1155 - n1156 - n1157 - n1158 - n1159 - n1160 - n1161 - n1162 - n1163 - n1164 - n1165 - n1166 - n1167 - n1168 - n1169 - n1170 - n1171 - n1172 - n1173 - n1174 - n1175 - n1176 - n1177 - n1178 - n1179 - n1180 - n1181 - n1182 - n1183 - n1184 - n1185 - n1186 - n1187 - n1188 - n1189 - n1190 - n1191 - n1192 - n1193 - n1194 - n1195 - n1196 - n1197 - n1198 - n1199 - n1200


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