New Zealand has to slow down. At least, that was the overall message from the NZ Transport Agency’s Mega Maps data released this week.

According to the online interactive tool assessing road trip risks, 95 percent of the country's 100 km/h roads should have a lower speed limit – with two-thirds of them slowing down to 60 km/h.

“We need to hit speed hard”, said Niclas Johansson, NZTA's acting director of safety and environment.

But without a proper cost-benefit analysis, that would be a fast decision heading for a crash.

Lower travel speeds mean higher costs for road freight, which covers 84 percent of land-based transport of goods. That means lower business productivity, penalising jobs and income creation.

Similarly, lower travel speeds mean prolonged household trips, of which 93 percent are made by private cars. That would unnecessarily hamper community mobility, damaging social and cultural connections within and between our regions, towns and cities.

Any political decision to lower speed limits should weigh the benefits of safety improvements against the costs on commerce and community. And that includes the costs and benefits of other options – particularly when three out of four road accidents are not related to speed limits.

For instance, more police enforcement of already existing road rules combined with public education campaigns are an effective – but often neglected – option.

Another option is to tackle traffic congestion, which significantly increases the likelihood of road crashes despite lower speed flows.

Additionally, a better road infrastructure would reduce road fatalities without putting a break on speed limits. (Our state highways are practically a misnomer, with only 2 percent of the network made up of dual-carriageway roads.)

A longer historical perspective too could avoid hasty – and costly – decisions. Notwithstanding the recent uptick in car crashes in the past five years, road fatalities per capita are currently a third of 30 years ago. Commendable progress has been achieved without tampering with speed limits during this period.

In short, New Zealand does not need to slow down to speed up an all-around road safety programme. As Johansson notes, “the information provided by Mega Maps is a starting point, not an end point.”

Rethinking speed limits may be part of the solution, but we should not ignore the other options on the table.

Meanwhile, better buckle up for a heated debate – but well worth it.