NZ Police Speed Detection Equipment documents

[sergei]

A while ago I made "Official Information Act" request to NZ Police regarding their speed detection equipment.
To be precise, this happened mid December 2014, when the NZ Police was threatening with 1km/h tolerance.
I wanted to know how really accurate is their equipment.

The most important bit, the accuracy table:


The response letter (I am not including the request letter, as it was a bit dry, I am lazy, and is quoted in response letter in italics):
http://sergei.nz/wp-content/uploads/2015/03/NZ_Police_Speed_Measuirng_Equipment_Letter.pdf

The "Speed Detection Equipment Operators Manual"
http://sergei.nz/wp-content/uploads/2015/03/Speed_Detection_Equipment_Operators_Manual.pdf

And finally the "Stalker Lidar EU Operators Manual"
http://sergei.nz/wp-content/uploads/2015/03/Stalker_Lidar_EU_Operators_Manual.pdf

I will post findings here: http://sergei.nz/nz-police-speed-enforcement-documents/ later.... I already found some small issues that make the stated accuracy in the table from above irrelevant.

[Stu-]

Interesting reading, thanks for posting

[sergei]

Here is why I think that 0.6km/h accuracy is pure and simply bullshit:
Directly quoted from the manual (bolded relevant parts):

Confirm patrol vehicle speed is consistent with the speed readout on the unit within +/- 3 km/h. This is achieved by travelling at a consistent speed, appropriate to the speed limit being operated in, and checking that the true speed(according to the certificate of accuracy) is the one displayed on the readout. Record the results in the logbook.

....


On a weekly basis the laser unit readout needs to be checked using a drive though by a patrol vehicle with a certified speedometer. This is carried out by having the driver of the vehicle drive at a steady speed towards the laser operation area. The speed will be relevant to the area of operation. The driver should flash their headlights or advise using the radio when the vehicle speed is steady and the laser operator will check the speed. The member using the laser will advise the vehicle driver of the results of the speed check, The driver will advise the speed they were travelling at after checking the certificate of accuracy to determine the true speed. Where the margin of error exceeds +/- 3 km/h the unit is to be withdrawn for servicing The results of the check must be recorded in the logbook (vehicle speed/checked speed). for example 64/65; 46/46; 75/75.

Just by going on this the accuracy of the units at any given day (except maybe the day it left the calibration facility) should be stated as +/- 3 km/h, disregarding the speedometer accuracy they are testing against! Which assuming is within 3km/h, the overall accuracy should be +/- 6 km/h (disregarding in added inaccuracy due to tyre pressure and wear).

[Akane]

Nice work.