Elderly man killed by car while checking mailbox

He'd lived an active life, travelling and volunteering, but an elderly Berowra, NSW, man was killed on Monday completing the most mundane of tasks.

Noel Rosten was hit by an out-of-control car as he checked his mail box, the female driver believed to be one of his neighbours.

As the driver was comforted near the wreckage of her crashed BMW, a few metres away stood the grieving widow of the man she had just run down and killed.

"The driver of the car has gone off the road and unfortunately a resident of one of the houses was in the driveway," Chief Inspector David Hogg said on Monday.

It happened around midday on Berowra Waters Road.

The woman, aged in her 50s, lost control on the bend, mounted the kerb and hit Mr Rosten.

A passerby walking her dog stopped to help, but there was nothing paramedics could do to save the 85-year-old grandfather.

Mr Rosten was active in the local community, known for his award-winning gardens and bush regeneration projects.

"He was into life, none of this sitting around watching TV," family friend Mick Marr said.

"He was into everything, you know, a good man, and he had such a big heart."

Locals have told 7 News the footpath was put in two years ago, despite protests from residents who said it was too close to the road.

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The crash investigation unit is yet to work out if it was driver error, a mechanical fault or wet weather that led to the crash.

"At this stage there is nothing to indicate that there was anything untoward was involved in the accident," Chief Inspector Hogg said.

The driver was taken to Hornsby Hospital for mandatory tests to see whether she was under the influence of drugs or alcohol.

Crash investigators will formally interview her in the coming days.

It's likely she will be charged with dangerous driving and negligent driving occasioning death.