U.S. Environmental Protection Agency

April 2001

Document Released for Public Information

"Trip Length Activity Factors for Running Loss and Exhaust
Running Emissions" 

Report Number   EPA420-R-01-013     (M6.FLT.005)
 
     The Office of Transportation and Air Quality, Assessment and
Standards Division announces the release of "Trip Length Activity
Factors for Running Loss and Exhaust Running Emissions" for
public information.  This document EPA420-R-01-013, also known as
M6.FLT.005, is available at the MOBILE6 section of the OTAQ Web
Site (http://www.epa.gov/otaq/m6.htm). 

     This document describes the data and a methodology used to
calculate running loss and exhaust emission length activity
factors.  The data used in the analysis were collected from two
instrumented vehicle studies.  These results are shown in tabular
form in the document.  The results include three distributions.
These are: (1) estimates for the number of vehicle trips per day,
(2) a distribution of trips by hour weighted by vehicle miles
travelled (VMT), and (3) the hourly VMT distribution by trip
length (in units of time).  In addition, the three distributions
were stratified by weekday and weekend.  The first two
distributions will be used in with the corresponding vehicle
running loss emission data in MOBILE6 to estimate hourly running
loss and exhaust emission rates. The third distribution - an
hourly VMT distribution by trip length was not used in the final
model because it was not consistent with the existing MOBILE5
running loss emission factors which were never updated in
MOBILE6.

     This report was originally released (as a draft) on February
18, 1998 under the title, "Trip Length Activity Factors for
Running Loss and Exhaust Running Emissions".  It was completely
revised in April, 2001 to accomodate the MOBILE5 based running
loss emission factors which were put in MOBILE6.  The original
draft document is now an appendix to the report. The April, 2001
is now the final version.  This final revision incorporates
suggestions and comments received from stakeholders during the
60-day review period and from peer reviewers.