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Traffic Volumes Data

Traffic Volume Maps 1994-2003: Additional Information

Data Collection Methodology

Data for TIG was collected in 15 minute intervals for the entire year (at "perm-count" sites) or periods typically 8 days long (at "short-count" sites). The data from perm-count sites formed the statistical basis upon which the summer average daily traffic (SADT) was derived. SADTs from the short-count sites were created by comparing the pattern of data for each short-count site to the most similar perm-count site. The result is an estimated average daily traffic volume for the months of July and August, rounded to the nearest fifty or hundred vehicles.

Data from two or more sites close to each other was sometimes aggregated to form a "composite count". In the simplest case, an SADT for two converging ramps at an interchange was 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 were added and/or subtracted to produce a new data set for a location at which no actual count was taken.

• Perm Counts: Permanent counts, or perm counts, are locations where traffic was counted on a continuous basis. They are identified by the characters "P-" in the code (eg. P-16-1)
• Short Counts: Short counts were collected for only a temporary period of time, typically 8 days during the summer

Accuracy

Traffic data for this application was obtained by remote automatic counting equipment which is subject to hazards. Data from these devices were carefully screened and adjusted to compensate for these infrequent events. Most of the count sites used induction loops to measure traffic volumes. A small percentage of special sites were counted using pneumatic hose.

The induction loop method records the number of vehicles passing over a series of metal wires buried in the roadway. The loops are not subject to wear and are less prone to failure, where pneumatic hoses typically overestimate the traffic volume by 10% or more.

Highway Direction

For simplicity, MoT assumes that highways in British Columbia are either north-south or east-west along their entire route. The major exception to this rule is Route 1, which is primarily east-west; on Vancouver Island, in Vancouver and in the Fraser River Canyon, Route 1's direction changes 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.

Application

This application is currently available to government users through the gww site with public access expected in June 2005. Government users may find the application here