Section 9: Vehicle Speed Data

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Vehicle Speed Data Collection

TPP collects vehicle speed data at approximately 44 sites (see Table 1-5) throughout the state for seven consecutive days twice annually. Where possible, TPP also collects speed data at WIM sites and at 130 directional AVC sites (not at intersections) for 48 hours annually. TxDOT uses permanent loop or piezo-electric sensors with leads in either a pedestal cabinet or small metal box attached to a guardrail or signpost to collect speed data. Speed data can also be collected with road tubes, but only at locations where there is no stop-and-go traffic.

National Maximum Speed Limit (NMSL) regulations require these data for safety certification. This legislation was repealed, but TxDOT monitors speed to assist in determining the effect of the repeal and the effectiveness of enforcement.

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Vehicle Speed Data Analysis

TPP categorizes vehicle speed data into speed bins or speed categories in 5-mph increments. Staff categorizes AVC sites by speed, type, and lane. At the 44 speed location sites (see Table 1-5 ), TPP categorizes data by volume and speed. TPP stores data by number of vehicles by hour and day within each speed bin and sums by volume within each bin.

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Vehicle Speed Data Reporting

TPP compiles the data semi-annually and makes it available upon request.

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