"I think it's still a bit worrying if every 10th question is wrong - that could mean potential confusion and problems."
He added that those who took 20 seconds to answer a question often did not have the luxury to do so in real-life situations.
The test is an extension of e-Drive, a website Mr Isler and his daughter created which includes more than 100 driving scenarios filmed on New Zealand roads. He saw the same concept as a safe and user-friendly way to prepare drivers for the new give-way rules.
"It puts people behind the steering wheel and shows them real video footage, so it's quite realistic."
Mr Isler planned to analyse another sample from this week's test results.
From 5am this Sunday, drivers turning right must give way to oncoming traffic turning left into the same street.
Drivers approaching the end of a road at a T intersection must give way to traffic turning towards them into the road.
Earlier this week, a Herald survey found most of the 67 people approached in Auckland, Hamilton and Tauranga knew the changes were coming - but just over half made at least one error in identifying which car should give way when they were presented with three test situations.
People can log on to www.giveway.govt.nzt and take an interactive quiz and view a computer drive-through animation illustrating how the two new rules will work.