Napier-Taupō Rd: NZTA Waka Kotahi using 'junk maths' to justify speed limit drop, traffic expert says 28 Apr, 2021 04:27 AM 5 minutes to read State Highway 5 from Esk Valley in Hawke's Bay to Rangitaiki, near Taupō, is one of NZ's most dangerous highways. Photo / Warren Buckland State Highway 5 from Esk Valley in Hawke's Bay to Rangitaiki, near Taupō, is one of NZ's most dangerous highways. Photo / Warren Buckland A Waka Kotahi NZ Transport Agency claim that a speed drop of 20 kilometres an hour on an 83km stretch of highway would delay commuters by an average of one minute has been labelled as "junk maths" and "disingenuous" by a traffic engineering specialist.