What Is Annual Average Daily Traffic (AADT)?
Unless you’re a traffic engineer, Annual Average Daily Traffic (AADT) may not be a metric you’re familiar with. However, it has a huge impact on the built environment around us. Take the following example: driving over potholes is never ideal, and it can get exceptionally frustrating when it feels like that pothole on your street has been there for ages! You might wonder what factors determine when a road gets fixed or how often it’s maintained. Of course, several elements come into play, and one of them is AADT; the subject of this blog.
What is Annual Average Daily Traffic?
AADT is a practical and relatively simple way to determine how busy a road is. It represents the total volume of vehicle traffic on a section of road or highway over a full year.
What is AADT used for?
There are many uses for AADT in traffic engineering and transportation planning. AADT is used to forecast needs for maintenance and highway and road improvements. It is also a consideration in determining where and what infrastructure gets funding. Going back to the pothole example, if the AADT of the road is lower than other roads in the area, it means less cars pass by each year; and it may be lower on the priority list for repairs.
AADT is applicable in circumstances where knowing how busy a road is over a year comes in handy. Picking the best location to open a business based on traffic levels in the area is one instance. For city planners, it provides insights into how new developments impact traffic congestion in an area by comparing the AADT before and after. It is also a useful metric for calculating emissions from road traffic, analyzing crash rates, and much more.
While there are several methods to calculate AADT, we will go over the two main ones. Using the ‘simple average method‘, calculating the AADT is simple if you have access to accurate and robust traffic counts. You must know the tally of vehicles that use the roadway in both directions every day during an entire year, then, divide that sum by the number of days in a year (365).
For many cities, however, continuous traffic data collection 365 days per year is impractical and costly. In fact, access to reliable, complete and accurate traffic data is a big challenge for many. As such, the second method, the American Association of State Transportation Officials (AASHTO) method, is commonly known as the averages of averages method. The AASHTO method uses a total of 84 averages: 7 averages corresponding to the days of the week for each of the 12 months in a year. The calculation requires daily volume counts on at least one of each day of the week for each month instead of every day of the year.
Overall the AASHTO method requires less data, however, the results won’t be as accurate. This is due in part to its assumption that every month has 4 weeks and an equal number of days of the week.
Two common methods of calculating AADT as outlined in the FHWA Traffic Data Computation Method Pocket Guide
Automating critical traffic metrics
Cities may spend upwards of $150,000 per year and countless hours to calculate their AADT. This is due to the amount of data collection, centralization, normalization, and manual calculation required. Luckily, there is a better, faster and cheaper way! UrbanLogiq is an example of a tool that automates the calculation of AADT and other important traffic metrics. Using the UrbanLogiq platform, public officials can automate metrics like Average Daily Traffic (ADT), Peak Hour Factor (PHF) and more in just a few clicks.
Example of ADT automatically calculated in the UrbanLogiq platform
AADT vs ADT
Annual Average Daily Traffic (AADT) and Average Daily Traffic (ADT) both measure how busy a section of road or highway is over time. A clue to how they are different is in the name. AADT refers to the average daily traffic volume at a given location over an entire year. ADT is the average daily traffic volume at a location over a period of time less than a year. For example, 6 months, a week, a month, a season, or only few days.
How UrbanLogiq helps
Get fast, timely insights from your data to better track mobility in your community. UrbanLogiq helps agencies move away from labor-intensive manual processes, centralize critical workflows, and get to insights faster. Contact us today to book a 30-minute demo at Urbanlogiq.com