AADT Calculation

How do you calculate Average Annual Daily Traffic (aadt)?

How to Calculate Average Annual Daily Traffic?

AADT is the abbreviation of Annual average daily traffic. It is the average vehicle traffic of one year on a highway. AADT is calculated by dividing the total volume of vehicle traffic on a highway for a year by 365 days. AADT is measured to determine the funding for maintenance and improvement of the roads.
Here is a brief tutorial on how to calculate AADT using the simple steps, knowing the total volume of daily traffic for the year.
How To Calculate Annual Average Daily Traffic
AADT = (Total volume of vehicle traffic for 1 year) / 365 days
Annual Average Daily Traffic aadt Formula
Measuring AADT and types of Daily Traffic:
There are two techniques used to measure AADT, one is Continuous count data collection method and the other is Short-term data collection method, also known as Coverage count data collection method.
→ Using Continuous count data collection method, sensors are permanently embedded into a road and traffic data is measured all 365 days.
→ Using Short-term data collection method, traffic is collected with portable sensors that are placed on the roads and traffic data is recorded for 2 to 14 days.
The traffic data collection sensors are devices which use radar, laser, or sonar technologies.
The Annual Average Daily Traffic (AADT) is measured every three years for the same road.

There are different types of measurements related to Daily Traffic, which are as follows:
→ Annual Average Weekday Traffic (AAWT) - Includes only Monday to Friday Data. Public holidays are excluded.
→ Average summer daily traffic (ASDT) - Data is collected during summer only.
→ Average Daily Traffic (ADT) - The average number of vehicles passing both to and fro, at a particular point of the road in a 24-hour period. Data collected for a year and divided by 365 days.

Lets consider an example,
What will be the AADT (Annual Average Daily Traffic) for a highway of 800 kms, provided the traffic data collected by the sensors say the total volume number of vehicles passing to and fro in a year on the highway is 4380546.
AADT Step by Step Calculation
Step 1: Assigning the given values
Total Volume of Vehicle Traffic for 1 year = 4380546AADT Example Calculation Step1
Step 2: Substituting the values in the formula,
Annual Average Daily Traffic (AADT)
= (Total volume of vehicle traffic for 1 year) / 365 days
= 4380546/365
= 12001.4 Vehicles / day
AADT Example Calculation
Hence Annual Average Daily Traffic (AADT) for that particular highway is 12001.4 vehicles per day.

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