The tag numlanes is defined as:
... Each lane is considered to be 1.7 meters wide. ...
I placed a few sample cars on a road with those lane widths and they just barely fit when parked, just don't try to open the door. Driving would be next to impossible, no margin for error.
In the US, standard highway lanes are 3.7m (12ft). Some roads go down to 2.7m (9ft). In the UK they vary between 2.5 to 3.35 (8.2 to 19.7ft)
Is 1.7m a typo or are roads in Oz really that narrow?
I think this section should read...
The centre of Carz traffic travels at 1.7m from the centre of the road (i.e. a road lane should be 3.4m wide to have Carz travel in the centre of a lane)