The ACT government has opened the floor for Canberrans to nominate sites across the city to place mobile speed cameras to curb speeding and improve road safety, roads minister Shane Rattenbury announced on Wednesday.

It's part of a move to add 100 extra mobile speed camera sites across the city.

Two new mobile speed camera vans were announced in the latest ACT budget, with four extra camera operators.

"Last year the ACT government announced it would expand the number of locations where mobile speed vans could be located, with a commitment to adding an additional 100 sites per year. This new website will provide a mechanism for the public to be directly involved in identifying the new sites," Mr Rattenbury said.

The $2.1 million investment was expected to yield $3.6 million in fines over the next four years.

Already the number of fines issued by mobile speed cameras doubled in the year to March 2016.

Canberrans can submit their nominations for a new mobile speed camera location on the new road safety cameras website.

To be approved, the site must be at least 200 metres from a change of speed limit unless it's near a school or work site.

The spot must also be clear of merging lanes, changes of road alignment or width and not cause any obstruction or line-of-sight issues to traffic flow.

The ACT government is also currently seeking input from Canberrans for a new number plate slogan.