Traffic Counts

Information about traffic volumes assists with planning, prioritising network improvements and with road design. This data is also valuable in assessing road safety, as well as helping to identify how effective past improvements have been.

We do approximately 250 counts per year through-out the district. Our traffic counting programme is carried out based on road hierarchy and need:

  • Low volume local roads (<200adt (average="" daily="" traffic))="" are="" counted="" every="" 13="">
  • Local roads (>200 ADT) are counted approximately every 5 years.
  • Collector roads* counted approximately every 3 years.
  • Unsealed roads are counted approximately every 10 years.
  • Primary or secondary arterial roads are counted approximately every 2 years.

New Plymouth District traffic counts (updated September 2018)

*Arterial roads are high volume roads like Tukapa Street and Carrington Street. Collector roads are key routes with lower traffic volumes like Seaview Road and Brooklands Road. Our road hierarchy is defined in our District Plan.

We don't count State Highways, these are done by NZTA and are available on their website or from the Traffic Counts website.

How traffic counters work

The counter unit is setup on the roadside with two tubes stretched across the road. The tubes are set out 1m apart. (This is to allow software to calculate the speed of a vehicle.)

As a vehicle drives across the tube it causes an air pulse to travel down the tube where its exact time (in microseconds) is recorded.

The counter records the pulses from each wheel (axle) of a vehicle. This information is downloaded into a file and we run this information through a software programme.

The software looks at the pattern of the air pulses from each wheel on the tubes. From those patterns, the software can tell the speed of a vehicle, how many wheels a vehicle has and the distance between each wheel.  The software defines the vehicles by the number of axles and the distance between them – for instance, a truck with two semi-trailers or a private car.

We leave the counter setup long enough so we get a minimum of seven full days of data.

Traffic count spreadsheet

The traffic counts are listed in the spreadsheet in alphabetical order, by street name. Each column is explained here:

  • Road name: The road the traffic count was carried out on.
  • Start Name: The name or description where the section of road starts
  • End Name: The name or description where the section of road starts
  • Location: the distance along the road in meters where the count was taken
  • Direction: Indicates which side of the road the count was on.
  • Latest: Indicates the latest count (Latest) or a historic count (Not Latest)
  • Count date: The start date that the count started.
  • Peak Traffic ADT: The volume of traffic counted in the peak hour during the traffic count
  • Peak Hour: The start time of the hour of the day with the peak traffic
  • ADT: the Average Daily Traffic (vehicles per day) based on a 7-day average
  • % Cars: Percentage of total vehicles counted that are cars
  • % LCV: Percentage of total vehicles counted that are light commercial vehicles (LCV).
  • % HRV: Percentage of total vehicles counted that are heavy commercial vehicles (HCV).


Traffic flow counts are variable due to various external factors, e.g. sensitivity of equipment, counting methods used, congestion effects and seasonal variations. The traffic flow data is intended to be used as an approximate indication of traffic volumes at counting sites.

People using the traffic count data should apply and rely upon their own skill and judgement when using the information, and consider the consequences arising from its use. The data should not be used in isolation from other sources of advice and information.