What do the numbers mean?
All Days (AADT) - This includes volume from all days of the week with no exclusions for public holidays or weekends.
Weekdays (AAWT) - This includes volume from Monday through to Friday. Three AADT figures are provided:
- AM Peak - Traffic volume during the hours of 6am to 10am.
- PM Peak - Traffic volume during the hours of 3pm to 7pm.
- Off Peak - Traffic volume during all hours of the day excluding 6am to 10am and 3pm to 7pm.
Weekends (AAWET) - Traffic volume for Saturdays and Sundays only.
Public Holidays (AAPHT) - Traffic volume from all days of the year defined as a Public Holiday (according to nsw.gov.au)
The Annual Average Daily Traffic (AADT) provides an estimate of traffic volume on a typical day of the year and is calculated as follows:
- Calculate the daily total for the each traffic collection station (365 figures).
- Calculate an average for each day of the week for each month (7 days x 12 months = 84 figures).
- Using the data from Step 2, create an average for each day of the week (7 figures, one each for Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday).
- Average the 7 daily averages from Step 3 to calculate the overall figure for the year, which is the resulting AADT.
The underlying data used to calculate the Annual Average Daily Traffic (AADT) is the hourly volume from each traffic collection station. This means each traffic collection station is expected to provide 24 observations per day. For the data provided to be considered reliable, it needs to pass through a number of data quality checks.
The first check is the regularity of data, quantifiable by at least 19 hourly observations per day. If it has not provided 19 hourly observations on a specific day, then that day is excluded from the analysis.
The second check relates to the consistency of the volume being recorded.
- At least one figure for each day of the week within each month is required (a minimum of 84 figures per year - 7 days x 12months).
- The daily volume from each traffic collection station is then compared to the average for that day of the week in the month. For example, Monday 3 June 2013 is compared to the average volume figure for all Mondays in June 2013. If the daily volume is greater or less than 20% of the average, that specific Monday is then excluded from the analysis, as the figure is considered inconsistent.
Note: When a traffic collection station is also a classifier, it will provide observations for a variety of different vehicle classes per hour, including light and heavy vehicles. It is possible to not have an observation in every vehicle class for every hour. To provide an indication of the data quality for the traffic collection stations that classify, the data quality check for the number of observations focuses on light vehicles only, as heavy vehicle observations can be intermittent during the day.