Driverless cars will be whizzing alongside commuters on the Tullamarine Freeway from this weekend, under a landmark trial of the new technology on Victoria's roads.

The luxury BMW, Mercedes Benz and Volvo cars will be driving in general traffic and they will also be tested in the Burnley Tunnel during routine closures.

But there is a disclaimer: people will be sitting behind the wheel. And on the open road, the drivers will be required to have one hand on the steering wheel, because it's illegal not to do so in Victoria.

They can drive hands-free, however, in the closed-off tunnels, where it is deemed safe enough.