Traffic Data
Accuracy
Statistical Preparation
Composite Counts
Highway Direction and Count Site Location
Copyright / Disclaimer
Contact Information
Traffic Data
The Ministry of Transportation compiles traffic data statistics each
year at specific spot throughout the province. Summary statistics such
as AADT (Average Annual Daily Traffic); SADT (Summer Average Daily Traffic);
AAWDT (Annual Average Weekday Traffic); AAWET (Annual Average Weekend
Traffic) are presented along with the specific data collected at each
site for each year presented. Traffic data for years prior to 1997 and
after 2003 may be available from other ministry sources.
Accuracy
Traffic data is obtained by automated counting equipment which is subject
to hazards. Data from these devices are carefully screened and adjusted
to compensate for these infrequent events. Most of the count sites use
induction loops to count the traffic volumes. A small percentage of
special sites are counted using pneumatic hose. The accuracy of the
data is subject to the precision of the data collection methodologies
and the statistical and theoretical strategies used in the projection
of short count data sites into annual statistics. The Ministry intends
to make 2004 and later traffic volume data available through a separate
website which is under development. There will be a significant difference
in that the 2004 and later data from short count stations will be linked
to the appropriate permanent count stations using the "factoring"
methodology whereas the pre-2004 data was linked by a 'best-fit' regression
analysis. Users of traffic volume data must be aware that as a result,
caution is to be used in analyzing time series data which spans the
Jan. 1 2003 "boundary".
Statistical Preparation
nformation is derived from data collected in 15 minute intervals for
the entire year (at permanent count sites) or typically 8 days (at short
count sites). The data from permanent count sites form the statistical
basis upon which the SADT's are derived. SADT's from the short count
sites are created by comparing the pattern of data for each short count
site to the most similar permanent count site. The information produced
is presented as an estimated average daily traffic volume for the months
of July and August.
Composite Counts
Where two or more sites are physically located close to each other,
data may be aggregated to form a 'composite count'. In the simplest
case, an SADT for two converging ramps at an interchange may be added
to produce an SADT for the ramp after the convergence. In the most complex
case, the raw data of two or more different locations are added and
/ or subtracted to produce a new data set for a location at which no
actual count was taken.
Highway Direction and Count Site Location
For simplicity, MoT assumes that highways in British Columbia are
described to be north-south or east-west. The major exception to this
rule is Route 1 on Vancouver Island, in Vancouver and in the Fraser
River Canyon where the primary direction is changed from east-west to
north-south. Exceptions also occur on Route 99 and Route 6. Descriptions
of count site locations are typically stated using direction and distance
from a cross road, municipality, bridge or other landmark. The direction
of the count locations from these landmarks will be in terms of the
predominant direction of the entire highway route and may not reflect
the true compass orientation of the highway at that location.
Copyright / Disclaimer
The material contained in this web site is owned by the Government
of British Columbia and protected by copyright law. It may not be reproduced
or redistributed without the prior written permission of the Province
of British Columbia. To request permission to reproduce all or part
of the material on this web site please complete the Copyright Permission
Request Form which can be accessed through the Copyright Information
Page.
Contact Information
Please forward any questions or comments to TrafficDataProgram@gov.bc.ca
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