But coroner Paresa Spanos, who last year investigated the deaths of three people killed in separate road crashes where the drivers at fault were impaired, has found Victoria's licensing system would be improved if health authorities directed greater attention to their patients' fitness to drive.

Under current laws, doctors are ethically but not legally compelled to report to VicRoads drivers who they think should not get behind the steering wheel because of mental-health problems or drug or alcohol use.

The system is instead reliant on drivers self-reporting to VicRoads.

Ms Spanos found drivers with problems were unlikely to report, as they often lacked the judgment to do so and reporting was against their own interest.

Ms Spanos did not outline how the licensing system should be improved, but said improvements were worth striving for.

She said better information-sharing resources among authorities would encourage more reports of drivers who did not belong on the road.

"At the very least, continued education of health professionals in all disciplines and specialties, by VicRoads in conjunction with the RACGP (the Royal Australian College of General Practitioners) and other professional bodies, is clearly warranted, to ensure that fitness to drive is at the forefront of practitioners' minds when a patient presents with symptoms or is diagnosed with a condition that is likely to affect their ability drive safely," she said in her findings, handed down on Monday.

The coroner's findings were drawn from her investigations into the deaths of:

* William Slater, 67, who died on December 27, 2006, when his car collided with a car on the wrong side of Princes Highway, Bairnsdale. The driver of the other car, Kane Miller, had been diagnosed with schizophrenia and later told an ambulance paramedic a man and woman were in his car "waving a knife around", the inquest heard. A judge later applied a permanent stay on criminal proceedings.

* Keiran Bailey, 44, a cyclist who was hit by Daniel Veerman on Mount Dandenong Road, Ringwood East, on March 8, 2011. Veerman drove across the bicycle lane at about 10km/h above the speed limit when he hit Mr Bailey, who died two days later. Veerman, the inquest heard, had been diagnosed with schizophrenia and a history of drug use. He was jailed for a minimum three and a half years in December 2011.

* Sean Brindle, 35, who was riding his bicycle on Beach Road, Mentone, when hit by a car on Christmas Eve 2008. Mr Brindle died three days later. The driver, Luke Shields, was speeding, drunk and drugged at the time of the crash. He had a history of drug and alcohol addictions and previous drink-driving convictions. He was jailed for a minimum 10 years in December 2009.

The inquest heard that of the 31,942 medical reviews VicRoads had performed on drivers in 2011-12, one quarter of the notifications came from the driver concerned.

Fifty-three per cent of notifications came from medical professionals, 10 per cent were from third parties, eight per cent came from police and four per cent were made by occupational therapists.