The Productivity Commission says national transport reforms must speed up as road freight is expected to grow by 50 per cent over the next two decades.

The report said creating national regulators and laws for the sector in 2011 was ambitious and has taken longer than anticipated.

Safety regulations of heavy vehicles, boats and trains have improved but commissioner Paul Lindwall said there is still "much more" to be done.

Mr Lindwall said action is needed to deliver forecasted productivity gains. He wants lower compliance costs for businesses and improved access to local roads for heavy vehicles.

Safety has continued to improve in the road and rail sectors following the reform.

Fatalities in the rail sector have dropped by 50 per cent over the past decade, while heavy vehicle crashes continue their long-term decline.

But the Heavy Vehicle National Law was labelled "inflexible", encouraging a "tick the box" attitude to safety.

Western Australia and the Northern Territory do not participate in the national heavy vehicle regime.

The commission recommended changing the grandfathering provisions that exempt some boats from national law as it poses a risk to safety.

It also doubts that small for-hire vessels such as tinnies and kayaks need to be regulated by the national body rather than state agencies.

Australian Associated Press