Road safety barriers have proved their worth, preventing almost 50 cases of potential serious injury and death in a year.

NZ Transport Agency figures show the flexible side and median barriers on the Cambridge section of the Waikato Expressway have been struck 48 times since it was opened a year ago.

NZTA's project delivery manager Peter Simcock said the flexible barriers are highly effective in reducing deaths and injuries for all types of road users, including motorcyclists.

"The flexible road safety barrier cables flex on impact, slowing the vehicle down and pushing it back into its lane.

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"We suspect many of these strikes on the safety barriers are caused by fatigue or inattention, and putting in the rumble strips is expected to reduce strikes and other potentially serious incidents," Simcock said.

The figure is expected to fall substantially when the final asphalt surfacing is complete and audio-tactile line markings, also known as rumble strips, are added.

Assumptions that flexible safety barriers have a "cheese cutter" effect and increase risks for motorcyclists are unfounded, said NZTA.

Evidence showed that installing flexible road safety barriers can have a beneficial effect and actually reduce motorcycle casualties.

This is because motorcyclists are more likely to survive an impact with a safety barrier than a crash with roadside hazards such as trees, poles and oncoming vehicles.

The final seal is currently being applied with the section closest to urban Cambridge completed last month. Rumble strips can then be added.

The 16km Cambridge section is likely to be completed in March.

The Cambridge section has produced peak-hour time savings of up to 23 minutes for a daily return journey between south of Cambridge and Hamilton, since it opened in December.

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Latest traffic monitoring shows the northern part of the Cambridge section is used by about 22,000 vehicles a day.