It is only a matter of time before someone is seriously hurt by NZ Post's electric delivery vehicles, the Postal Workers Union says.
Official figures show the electric vehicles, known as Paxsters, have been involved in 34 crashes - four during a trial period in 2014 and 2015, and 30 since they were rolled out in larger centres last year.
There are now 50 Paxters in use after New Zealand Post spent $15 million on the vehicles, which were imported from Norway.
Figures showed the crashes were collisions with people or objects but NZ Post said there have been no reported injuries to members of the public.
Postal Workers Union southern district president John Maynard said posties were allowed to drive the vehicles up to 20km/h on footpaths.
He said Paxters were silent and did not have good rear vision.
And he said posties were working long hours and were often fatigued and he was worried about what could happen.
"We don't think the company's firstly, had enough time to select the correct vehicle ... so we're really concerned about that, but also about the taking up of the footpaths and the danger of a collision.
"As the company puts pressure on posties about productivity we're worried about people driving them quite fast."
The union is in a dispute with NZ Post over safe rosters for operating the vehicles.
The vehicles can carry up to 200kg, have a range of up to 90km and have a road speed of 45km/h.