Police are critical of bus maintenance standards after finding mechanical faults in more than a third of buses inspected during a roadside check last week in Canterbury.
Of 37 buses heading to the Kaikoura Trotting Cup, six were ordered off the road.
One had a critically worn driveshaft, while another had a failed rear suspension support and a third was leaking diesel.
Other buses had cracked windscreens, bald tyres or were overloaded.
Police say the checks show some bus operators are putting their passengers at risk.
