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Southern mayors have also raised worries about reliance on speed-limit reductions to reduce harm on roads and under-investment in the network, driver education and speed enforcement.
National transport policy appeared to prioritise urban concerns over the needs of rural communities, they said.
Both Transporting New Zealand chief executive Nick Leggett and Automobile Association Otago chairman Malcolm Budd hit out at what they see as a national campaign to cut speed limits from 100kmh to 80kmh on state highways that lack median barriers.
That would affect the vast majority of Otago and Southland state highways.
Mr Leggett called on the Government to be transparent with the public about its agenda.
The Ministry of Transport has said there are no current or planned proposals for a sweeping policy that would reduce speed limits on roads without median barriers.
The NZ Transport Agency said the agency, the ministry and the Government "have all been very vocal about the role of safe speeds in helping New Zealand achieve the 40% reduction in deaths and serious injuries by 2030 set as an initial goal in the Road to Zero strategy".
The agency is working through a series of speed limit reviews.
Most of Northland’s 880km of state highway could have speed limits slashed from 100kmh to 80kmh.
Those proposals have been labelled "punitive".
The speed limit on a 90km stretch of State Highway 5 between Napier and Taupo is to be cut from 100kmh to 80kmh next month.
Road users there have said this could lead to impatient drivers attempting risky overtaking manoeuvres.
There is also a speed limit review under way on the stretch of SH2 from the Hutt Valley in Wellington to Featherston in Wairarapa.
However, lowering the speed limit on sections of SH6 between Nelson and Blenheim at the end of 2020 has been labelled a success by officials.
The serious crash rate was slashed.
Gore Mayor Tracy Hicks was wary of a one-size-fits-all mentality.
"If there was to be some kind of blanket lowering of speed limits, I think that would go down badly," Mr Hicks said.
Waitaki Mayor Gary Kircher said the South did not do as well as other regions from national policies directing transport funding to regions where traffic was busiest and where emphasis had shifted to public transport and cycling.
Queenstown Lakes Mayor Jim Boult said wholesale speed-limit changes would not necessarily achieve safety objectives.
Mr Leggett said Otago and Southland were a "poor cousin" for receiving lower levels of roading investment.
Mr Budd said money needed to be spent on upgrading roads and speed-limit reductions should be considered on a case-by-case basis.
An adjusted philosophy for speed management is outlined in a 2018 Ministry of Transport document.
In it, officials signal their lack of comfort about "misalignment" between speed limits and road conditions, in many cases.
Many people travelled too fast for the conditions, "because the posted speed limit does not reflect the level of risk".
Ministry of Transport mobility and safety manager Robert Anderson said the ministry expected to make progress this year on tackling unsafe speeds.
The programme’s main components included moving to safer speed limits around schools.
A new regulatory system for speed management would be established, "improving the way road controlling authorities plan and implement speed limit changes through introducing speed management plans".
A spokesman for the transport agency said it was reviewing speed limits on high-risk sections of New Zealand’s state highway network and locations where communities were calling for safer speed limits.
"Where evidence gathered from these reviews shows that speed limits are not safe and appropriate we are proposing new safer speed limits."