Rail planners have been urged to think more strategically about fast train technology and the protection of potential south-east Queensland transport corridors from developers.

The Queensland government last week confirmed it was backing the eight-lane Coomera Connection as a secondary M1 route to the Gold Coast, but public transport lobby group Rail Back on Track's spokesman, Robert Dow, said planners should not automatically jump to adding more lanes to the region's highways.

"What we are trying to highlight is that we need to get very serious at this point about our fast train options, not only on the Gold Coast but on the Sunshine Coast as well," he said.

Rail Back on Track has put forward a futuristic idea to build a 160km/h elevated rail line along a section of the M1 between Beenleigh and the Cross River Rail at Dutton Park "to stimulate debate, not necessarily roads".