THE RULES – WHAT A COF 
TRAILER MUST HAVE:
Certified heavy vehicle brakes
Heavy trailers first registered on or 
after 1 July 2008 generally require 
brakes matched and certified between 
the tow vehicle and the trailer.
Engineering certification
The design and build must be signed 
off by a heavy vehicle specialist 
certifier (LT400) before the trailer 
can be certified for the road.
Six monthly COF inspections
At an approved heavy vehicle 
inspection site, and the trailer must 
be always kept at COF standard.
Road user charges (RUC)
Heavy trailers pay distance-
based RUC, bought in 1000km 
blocks, like any heavy vehicle.
ROADSIDE CHECKS WHAT 
THE POLICE CAN DO
Under section 125 of the Land 
Transport Act 1998, Police can 
require any vehicle they suspect may 
be a heavy vehicle to stop and be 
weighed.  If a loaded trailer appears 
to be at or over 3,500kg GVM, even if 
it is registered as a WOF (light) trailer, 
it can be pulled over and weighed.
The Police can weigh the full 
combination or separate the vehicles 
and weigh each independently to 
check compliance against GVM 
or gross laden weight. Unsafe 
loading is also an offence under 
sections 6 and 9 of Land Transport 
Act 1998, enforceable by Police 
regardless of whether the vehicle 
is classified as light or heavy.
EXAMPLE: RAM 2500 + BALEX 770 COF TRAILER
RAM 2500 GVM
4495kg
Trailer GVM (Balex 770 COF rating)
4500kg
RAM 2500 combination 
mass (GCM)
11437kg
RAM 2500 max braked 
tow coupling rating
6942kg (pintle hook) / 
4500kg (70mm ball)
Max vertical coupling 
load (noseweight) — 
450kg (check your manual, typically 
max 10% of braked tow rating)
Feature
58  FISHING IN GODZONE MAGAZINE
This Balex Trailer 770 is COF-
rated to 4,500kg and paired 
with the client’s RAM 2500.

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