The deadline for submissions on the government's Safer Roads strategy was due to close yesterday, but the Department of Infrastructure, Energy and Resources has decided to extend that until December 14.

A department spokeswoman said the extension would allow briefings to be provided to councillors, as well as council staff, and time for them to prepare submissions in consultation with residents.

"Councils now have until December 14 to nominate any roads, or sections of roads, which they believe meet the criteria for 100km/h (speed limit)," she said.

The strategy aims to prevent crashes on country roads by reducing the speed limit on gravel roads to a maximum of 80km/h and the limit on sealed rural roads to 90km/h, unless they meet a list of criteria.

At the strategy launch, Infrastructure Minister David O'Byrne said research showed that reducing 100km/h speed limits could reduce the number of serious crashes on Tasmanian rural roads by more than 40 per cent.

Local Government Association of Tasmania chief executive Allan Garcia said councillors and residents were divided on the issue.

"Councils want to make sure their communities understand what is being proposed and that there is an opportunity to look at the roads, or parts of roads, where the current speed limit (of 100km/h) could be retained," he said.

Western Tiers MLC Greg Hall has flagged his intention to set up a parliamentary inquiry into the proposal after residents raised concerns.

Results of the department's preliminary road assessments and the rationale will be presented to councils early next year.