Following two fatal crashes in the Waikato this month, the district's police commander is urging driver to watch their speed after a crash claimed the life of a man on the outskirts of Thames this morning.

Superintendent Win van der Velde says emergency services were called to the scene of the crash on Parawai Rd about 4.25am.

Police are asking people to slow down the roads.

'The crash is still under investigation by the Serious Crash Unit but initial indications are the 37-year-old female driver of the Holden Commodore lost control of the vehicle and left the road, crashing through three fences.

'There were five people in the car at the time and one of them, an 18-year-old male travelling as a rear seat passenger, died in the crash.”

Win says it's particularly concerning for police that earlier that morning, about 1.30am, officers stopped the same car being driven by a 31-year-old man who failed a breath alcohol test and the vehicle was found to be unroadworthy.

'It was issued a non-operational order and the keys were taken by police so it should not have been on the road at all, let alone being driven at the time of the crash.”

This morning's crash brings the number of people killed on Waikato roads this month to two, twice the number killed for the same period last year and is the sixth fatal or serious injury related crash attended by members of the Waikato Serious Crash Unit this week.

One officer returning from one of those crashes, where several people were seriously injured near Cooks Beach on Tuesday stopped a 49-year-old woman motorcyclist travelling at 151km/h.

'And last night officers attended a head-on collision on SH24 south of Matamata where a vehicle lost a rear wheel and crashed into an oncoming car leaving one person suffering critical injuries, another in a serious condition and two others with moderate injuries.

'Each of this week's crashes has occurred on rural roads and police are becoming concerned that drivers are becoming too complacent.

'Only this morning I stopped a car doing over 120km/h on a rural road and yesterday one of my Constables stopped two eastbound vehicles on SH25A in the Coromandel travelling at speeds of 152 and 148km/h while overtaking.”

Win says such speeds at any time, let alone over the holiday period with extremely high traffic flows, are unacceptable and the police's zero tolerance of vehicles travelling at speeds more than 4km/h over posted speed limits has been well advertised.

'When you get behind the wheel of a vehicle you have to make some conscious decisions, am I sober enough to driver, am I well rested enough not to be effected by fatigue, am I travelling at a safe enough speed and to the conditions and if you answer know it's probably the same answer to the question- should I be driving at all?”