Sleep loss during the daylight saving transition

On Sunday 27 September, New Zealanders will put their clocks forward an hour for daylight saving. We know we’ll lose an hour’s sleep. What we may be less aware of is what happens on our roads afterwards. 

New Zealand research analysing 12.6 million ACC accident claims between 2005 and 2016 found road accident rates were 16% higher on the first day after daylight saving began and 12% higher on the second. 

We know fatigue can seriously impair reaction time, attention, judgement and decision-making.  Every September we hear the familiar advice: get enough sleep, take extra care and don’t drive tired.  

But in 2026, there’s another dimension worth considering: we have never had more information about ourselves. Technology is increasingly telling us things about our health and behaviour that we might not otherwise have known. 

However, the answer isn’t as simple as trusting your smartwatch. Treat that information as part of a bigger picture. Consider: how much sleep did you actually get? How long have you been awake? What time of day are you driving? How do you feel? 

People whose driving performances are particularly vulnerable to sleep loss won’t necessarily recognise the extent of that deterioration themselves. 

We must normalise changing plans when those signals tell us something we don’t want to hear, whether that’s delaying a journey, sharing the driving, stopping for a short nap or calling someone for a lift.  

Saying “I’m unfit to drive” due to tiredness should be seen as good judgement, and we need to exercise that whenever we drive, not just when daylight saving begins. 

Credit: Thanks to Charles Dawson and our friends at AutoSense who provided the majority of the information behind this article.

Read more: Fatigue Management Road Freight Update