Page 44 - TransportationPlanUsetsGuide

Table 3.2: Traffic Volume Comparison – 2007 and 2012
Urban Area 1 Rural Area 2
Volume Percent Volume Percent
2007 2012 Change Change 2007 2012 Change Change
Average Auto Volume 13,398 12,936 -462 -3.45% 6154 5,971 -182 -2.96%
Average Truck Volume 762 744 -18 -2.33% 646 565 -81 -12.52%
Average Percent Trucks 5.66% 5.56% -0.10% 11.28% 9.71% -1.57%
1 Based upon 211 counts containing data for both 2007 and 2012.
2 Based upon 53 counts containing data for both 2007 and 2012.

Vehicle Miles Traveled (VMT)
VMT is a useful way to measure overall utilization of the transportation system. The U.S. Department of Energy reports
annual VMT per capita. ODOT estimates VMT on state routes by county; estimates for Washington County are shown in
Figure 3-4. Some of the decline in VMT on ODOT facilities may be due to the transfer of some facilities from ODOT to
Washington County, and some may be due to the economic downturn during the period from 2007-2011. Fuel sales are
another way to estimate VMT. Figure 3-5 shows fuel sales per capita in Washington County between 2006 and 2011,
which have declined during this period.

For the TSP, VMT was
computed using output
from Metro’s regional
travel demand model. The
primary advantage in us-
ing the regional model is
that it allows the forecast
of VMT into the future, and
allows for comparison of
VMT between transporta-
tion system alternatives.
The primary disadvantage
is that the regional model
output is not available for
each year. Therefore the
evaluation cannot show
trends over time, only
the absolute change at
the end of the planning
horizon. Historical VMT
numbers and trends can-
not be calculated consis-
tently from this data. In ad-
dition, the regional model
is only valid for the specific
level of land use develop- Traffic on Pacific Highway in Tigard
ment included in the adopted regional forecast, and cannot be used to test alternative land use scenarios that might be
developed at the county or local levels. Given these limitations, additional national and local information was used to
further analyze VMT for Washington County.

34 PART 3: TRANSPORTATION MODAL ELEMENTS
Effective November 27, 2015 • Updated December, 15 2016