Section 7: Vehicle Classification Data
Anchor: #i1105037Vehicle Classification Data Collection
TPP makes vehicle classification counts at 650 to 750 locations (see Table 1-2) across the state each year. (To see a map of TxDOT districts, link to http://www.dot.state.tx.us/local_information/default.htm.) The number of sites counted each year varies according to the condition of the road counting hardware installed at the sites to collect the data with automated vehicle classifier (AVC) equipment. The number of special requests for vehicle classification counts also affects the number of sites. At AVC sites, TPP has sensors and a loop embedded in the roadway with a cabinet on a pedestal to house the electronics, loop, and piezo sensor leads. If there are problems at the site (construction, bad sensors, or loops), TPP must either repair the equipment or schedule a visual classification contract to collect the data. At locations where there is no stop-and-go traffic, TPP may choose to collect vehicle classification data with road tubes.
Click on district name to access location listing |
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There are three types of vehicle classification data collection:
- automatic (AVC) at approximately 250 sites with 48-hour data collection
- contract visual classification counts at approximately 400 sites with 24-hour data collection
- telemetry (AVC) at 25 border sites with data collection 365 days a year.
TxDOT makes the counts using the currently installed equipment. Where equipment is not available or not suitable, contractors make visual classification counts.
Counts consist of 24-hour samples (midnight to midnight) that categorize vehicle types into 13 classes and unclassified (see Table 1-3 which links to individual figures).
Classification Code |
Vehicle Type |
Link to Figure |
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1 |
Motorcycles, passenger vehicles, and small or short-wheel-based pickups |
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2 |
2 axles, 4-tire single-unit trucks (full-sized pickup trucks) |
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3 |
Buses (2 and 3 axles) |
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4 |
2-D, 6-tire single-unit vehicles (includes handicapped-equipped and mini school buses) |
|
5 |
3 axles, single-unit vehicles |
|
6 |
4 or more axles, single-unit vehicles |
|
7 |
3 axles, single trailer (2S1) |
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8 |
4 axles, single trailer (2S2 or 3S1) |
|
9 |
5 axles, single trailer (3S2, 3S2 split, or 2S3) |
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10 |
6 or more axles, single trailer (3S3, 3S4, etc.) |
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11 |
5 or less axles, multi-trailers (2S1-2) |
|
12 |
6 axles, multi-trailers (2S2-2 or 3S1-2) |
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13 |
7 or more axles, trailers (3S2-2) |
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14 |
Unclassified (AVC and WIM) |
None |
Anchor: #i1105092
Vehicle Classification Data Analysis
TPP uses vehicle classification data in combination with overall volumes to develop a percent of vehicles within the 14 classes (Table 1-3). This information establishes the number of trucks that subsequently is reported as the percent of single and combination trucks in HPMS. TxDOT also uses these data to develop equivalent single axle load (ESAL) calculations for pavement design and to estimate percent of trucks for design, operation analysis, and environmental documentation.
Anchor: #i1105102Vehicle Classification Data Reporting
TPP publishes the vehicle classification report annually, generally at the end of the fiscal year. The report summarizes the number of vehicles in each of the 14 classes (Table 1-3) at each count location.