Extra buses from Brisbane's western suburbs - from Kenmore, Riverhills, Chapel Hill and Mt Ommaney - will run through the Legacy Way tunnel from January, saving thousands of commuters up to 13 minutes each morning and afternoon.

It also means students of Brisbane's Boys Grammar and Girls Grammar schools who live in Brisbane's western suburbs or QUT's Kelvin Grove campus can now catch the bus straight to school or university.

Thew news has been welcomed by Robert Dow, a spokesman for public transport lobby group Rail Back on Track, which has pushed for extra buses through the Legacy Way tunnel since 2012.

"It is a long-term promise that has been left hanging, but it is good to see that something has finally happened," Mr Dow said.