For locations under construction or not yet in existence, the Transportation Planning and Programming Division (TPP) estimates the anticipated average daily traffic (ADT) volumes at the district’s request. To aid TPP in making such an estimate, 24-hour machine counts should be made along each approach open to traffic. An up-to-date map of the area and a layout of the location as it will be constructed should also be provided. (If construction will be staged and the location opened to traffic in increments, layouts at various stages of construction are recommended.) If a major traffic generator (shopping center, industrial plant, recreational facility, school, etc.) is in operation (or expected) within a 0.5 mile radius of the location, the information should be included in the request to TPP.

Using the projected ADT volumes, the following general guidelines can be used to obtain an estimate of vehicle count data:

The maximum 8-hour volume

is generally between 50 percent and 60 percent of the ADT, with the average being approximately 52 percent. In an urban area with a high ADT, the percentage is generally between 55 and 60 percent.

The average hourly volume

of the maximum 8‑hour volume is generally between 6 percent and 8 percent of the ADT (maximum 8‑hour volume divided by eight.)

The lowest hourly volume

(eighth highest hour) of the maximum 8‑hour volume is generally between 5 percent and 6 percent of the ADT with an average value of approximately 5.5 percent. It is also approximately 80 percent of the average hourly volume or 10 percent of the maximum 8‑hour volume. This value is the basis for comparing the anticipated volumes with the volume warrants for signalization found in the

Texas Manual on Uniform Traffic Control Devices

(TMUTCD).

The lowest hourly volume

(eighth highest hour) for a “grid system” of existing signals within a city is assumed to be 5 percent of the ADT.

The peak hour volume

(highest hour) is generally between 6 percent and 10 percent of the ADT. The lower values are generally found on roadways with low volumes. The average value is approximately 8.4 percent of the ADT.