Section 7: Vehicle Classification Data

Anchor: #i1105037

Vehicle 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 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.

Anchor: #BGBEAHFDTable 1-2: Vehicle Classification Count Locations by District (Incomplete)

Click on district name to access location listing

Abilene District

Dallas District

Paris District

Amarillo District

El Paso District

Pharr District

Atlanta District

Fort Worth District

San Angelo District

Austin District

Houston District

San Antonio District

Beaumont District

Laredo District

Tyler District

Brownwood District

Lubbock District

Waco District

Bryan District

Lufkin District

Wichita Falls District

Childress District

Odessa District

Yoakum District

Corpus Christi District

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).

Anchor: #BGBJGFHFTable 1-3. Texas Vehicle Classification Scheme

Classification Code

Vehicle Type

Link to Figure


Motorcycles, passenger vehicles, and small or short-wheel-based pickups

Figure 1-1


2 axles, 4-tire single-unit trucks (full-sized pickup trucks)

Figure 1-2


Buses (2 and 3 axles)

Figure 1-3


2-D, 6-tire single-unit vehicles (includes handicapped-equipped and mini school buses)

Figure 1-4


3 axles, single-unit vehicles

Figure 1-5


4 or more axles, single-unit vehicles

Figure 1-6


3 axles, single trailer (2S1)

Figure 1-7


4 axles, single trailer (2S2 or 3S1)

Figure 1-8


5 axles, single trailer (3S2, 3S2 split, or 2S3)

Figure 1-9


6 or more axles, single trailer (3S3, 3S4, etc.)

Figure 1-10


5 or less axles, multi-trailers (2S1-2)

Figure 1-11


6 axles, multi-trailers (2S2-2 or 3S1-2)

Figure 1-12


7 or more axles, trailers (3S2-2)

Figure 1-13


Unclassified (AVC and WIM)


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: #i1105102

Vehicle 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.

Previous page  Next page   Title page