The number of NZ Post buggy crashes tripled last year, with almost 250 reported incidents, including two that led to serious injuries.
Figures released under the Official Information Act show the e-vehicles, known as 'Paxsters', crashed into cars, fences and road signs.
There were 249 crashes in total with the majority involving a Paxster hitting or being hit by a vehicle or object, up from 82 in 2017.
The number of injuries to posties also more than doubled last year, from 36 in 2017 to 80 in 2018.
Two of these injuries were serious and required professional medical treatment, but an NZ Post spokesperson said severity of the injuries was less than those in bicycles.
"We have seen declining costs associated with injuries since the introduction of Paxsters, this suggests injuries are less severe in nature than traditional bicycle.
"We believe this is attributable to the stability of a four wheel vehicle versus a two wheel, more efficient braking, greater visibility and more robust protection offered by a Paxster versus a Bicycle."
The spokesperson said all posties completed a "comprehensive training programme" before operating Paxsters, and safety briefs were issued when trends were detected.
"It is also important to note that we work closely with local councils before we start using the Paxsters in any area, and only operate them in areas where we have been given permission."
Introduced in 2016, the buggies make up the largest road-worthy e-vehicle fleet in the country.
The fleet began with 54 vehicles in July 2016 and grew to 423 last year.
There have been a number of complaints to NZ Post about Paxsters, the number peaking in July 2018 at 31 complaints.
Among them were complaints about Paxsters damaging the grass berm, being reversed into other vehicles and being driven at alleged excessive speed on the footpath.