Motorists should pay 'per peak kilometre'

Motorists should be taxed for every kilometre they drive in peak hour, a transport expert says.

Professor David Hensher, director of the Institute of Transport and Logistic Studies at the University of Sydney, will be a key speaker at the NSW Transport Infrastructure Summit in Sydney on Wednesday.

He'll join NRMA director David Bentham and City of Sydney transport strategy manager Terry Lee-Williams to discuss ways of easing traffic congestion.

Prof Hensher believes that dumping the registration charge and fuel excise, and charging motorists for when they drive will ease congestion and lead to a fairer system.

The institute's plan to overhaul the current roads tax system is also outlined in a document tabled at the federal government's tax forum on Tuesday.

"People pay the same amount to register the same vehicle, but some people might travel 15,000km a year and others might travel 10,000," Prof Hensher told AAP on Tuesday.

"It doesn't seem fair to pay the same amount for different degrees of use of the road network."

Under the proposals, motorists would instead pay as much as 15 cents per kilometre they drive in peak hours, dropping to about 5 cents/km during off-peak hours.

"Kilometre-based charging is a mechanism for recognising that those people who travel at times when there's high level of congestion should actually pay more than those people who travel at times when there's no congestion," Prof Hensher said.

But he rejected the term congestion tax, saying it is not about paying another tax.

"At the end of the day, the charge is only an efficient charge if it delivers positive benefits through time savings, so the objective is really to try and make more efficient use of the road network."