Speed behind biker deaths, say police

'Twit' motorists and 'born-again' older motorcyclists among reasons for high accident rates, expert claims.

A spate of motorcycle fatalities has prompted police to warn riders to reduce speed. And an expert claims motorists can be "twits" after at least four riders were killed and several critically injured in as many weeks.

In the latest crash, a 45-year-old motorcyclist was killed when he hit the back of a 10-tonne tractor trailer as the unit turned into a driveway on a rural road near Morrinsville on Saturday morning.

Less than 90 minutes later at 11am another motorcyclist on a charity ride at Ohinewai, east of Huntly, was critically injured when he failed to round a bend and crashed into a fence.

The accidents come a day after a mechanic in his 60s was badly injured when his motorbike and a car collided in Whangarei.

Four days earlier, on February 24, Christiaan Minnee, 36, died in hospital after colliding with a turning ute at Tamahere in Waikato, and on February 20, 72-year-old Jack Barnes of Hamilton died when his motorcycle and a car collided on the Brynderwyn Hills south of Whangarei.

The year's first fatal motorcycle crash happened in Taupiri at 10pm on January 4, when Auckland-based Chinese national Shixun Jiang, 24, crashed into an oncoming car as he tried to overtake traffic on State Highway 1B.

Speaking after Saturday's death on the Morrinsville-Walton Rd, Waikato road policing manager, Inspector Freda Grace, said police were concerned at the number of motorcyclist fatalities this year and urged riders to be cautious.

"The circumstances of this crash mirror those of a crash earlier last week that claimed the life of another rider and appears to be another avoidable tragedy," she said.

Mrs Grace said speed appeared to be a factor in both Waikato crashes on Saturday.

New Zealand Motorcycle Safety Consultants chief executive Allan Kirk said motorcyclists must always be prepared for the worst to happen.

"It's an equal amount of stupidity and unfortunate luck that comes into these crashes," Mr Kirk said.

"The driver simply doesn't see them for a variety of reasons. Therefore the motorcyclist has to be able to second-guess what that driver is going to do. In other words, be prepared for right twits."

Mr Kirk, who has been riding for 50 years, said New Zealand had a problem because many riders aged over 40 lacked experience.

"They're what we call born-again bikers who came back into riding.

"They were quite capable of controlling a bike in the old days, but bikes these days have improved so dramatically that now the bike can outride the rider. And these guys are getting into trouble."

Mr Kirk said many older riders did only about 2000km every year during summer, and that wasn't enough riding experience.

"They tend to lose the edge."

Another problem was target fixation, in which riders focused too long on something they wanted to avoid and instead ran into it.