Good point about the traffic calming. It appears to me that NZ is really reluctant to put in traffic calming measures. Apparently in the Netherlands ( I have not looked up other countries) over 45% of residential streets are 30 Kmh zones ( https://www.swov.nl/rapport/Factsheets/UK/FS_Residential_areas.pdf ). I have serious doubts about whether a 30 kmh sign alone will do the trick. I think it is not unlikely that those drivers who are careful around cyclist anyway will stick to the 30 kmh while the less careful driver will disregard the signs if there is not enough traffic calming.