It's been revealed wheelchair users may not be able to be evacuated quickly from buses on the new O-Bahn tunnel through the parklands in the event of an emergency.
Advocates say the gap between bus lanes and the tunnel walls is too slim.
A letter to bus drivers states that they may need to carry passengers to an emergency walkway if their wheelchair is too big.
It's prompted calls for the Government to overhaul its safety features.
But Transport Minister Stephen Mullighan says the tunnel provides “adequate space for wheelchair ramps to be lowered, allowing access to exits in an emergency”.