The minimum passing distance law, being pushed by the Victorian Greens, was also coolly received by VicRoads and the Transport Accident Commission due to a lack of hard evidence that it would make the roads safer.

The TAC's senior manager of road safety, Samantha Cockfield​, also argued that compelling motorists to give cyclists a one-metre buffer when overtaking would increase tension on the road.

"The biggest concern for us all is that introducing a law where people can't always easily comply may bring about more tension in a system where there is a lot of tension already between motorists and cyclists," Ms Cockfield said.

Recent market research by the TAC identified real tension on the road, Ms Cockfield said, with cyclists concerned about being hit at intersections or targeted by an angry driver, and motorists concerned by cyclists who run red lights and ride unsafely.

Victoria is considering following other states that have changed their road rules so motorists must leave a one-metre gap when overtaking at speeds of 60km/h or less, and 1½ metres at higher speeds.

Queensland and South Australia have already introduced minimum passing distances, and NSW, Tasmania and the ACT are trialling the law.

Victoria's road rules state that drivers must leave "sufficient" passing distance when overtaking bicycles.

The Greens are pushing for legislation that would specify a safe passing distance of at least one metre.

But the law change was firmly opposed by Victoria Police on Monday, which gave evidence before a public hearing of Parliament's Economy and Infrastructure Committee that the case is deeply flawed.

Acting Senior Sergeant Ryan Burns said at the hearing that the law would require motorists to cross white lines, potentially putting them in the path of an oncoming vehicle. It would be particularly dangerous on roads shared with trams, and on narrow rural roads with 100km/h speed limits, Mr Burns said.

He also argued that it would be "difficult to detect and easy to contest", because it would rely on a police officer's "subjective" assessment that the buffer had been breached.

It also emerged from police evidence that just 50 police vehicles in Victoria have in-car video cameras, following suggestions these cameras could be used to gather evidence that a car had passed a cyclist at an unsafe distance.

So far there is no data from the other states that have brought in minimum passing distance laws that indicates less road trauma, Mr Burns said.

VicRoads is also wary of changing the law until it sees more evidence, but was questioned by Greens MP Colleen Hartland over an inconsistency in its stated position.

The authority's learner driver's licence handbook already recommends drivers leave a minimum gap of at least one metre when overtaking cyclists.

"Why not have it as law when it's what you already recommend?" Ms Hartland asked.

Robyn Seymour, VicRoads' director of Vehicle and Road Use Policy, said while that had long been the recommendation, there was not yet enough evidence to change the law.

Both VicRoads and the TAC would consider revising their positions if results from other states showed safety was improved, the hearing was told.