Heavy fog yesterday morning sparked a major police presence to ensure driver safety after a minor nose-to-tail crash on SH2 just south of Masterton.

Police road control was widely deployed near Norman Ave about 8am with visibility down to 50m, while police eased two damaged vehicles into a layby.

One driver, who declined to be named, said the car in front of him braked suddenly.

"Traffic was piling up here, and he braked very heavily," he said.

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"I managed to avoid the car in front, but the car behind me couldn't avoid me."

No one was injured in the crash.