LO3X / VO3X / VSO / B9TL - 2nd axle is tag axle
Trident / K310UD / MAN 24.310 - 3rd axle is tag axle.
Basically the drive axle will be the axle with the hub in
it.
Adding on to the above information, turning (or rather, active)
tag (or lazy) axles are present on the LO and VO 3-axle buses, but
discontinued from the Super Olympian onwards. This was due to
simplification in design and allowing a lower floor
configuration.
For third axle tag designs, the above three examples do not have
steering features, but the Neoplan Centroliner has this turning
feature, and activates between 20 to 45 km/h.
Power axles are easy to identify with twin tires being the one,
or if you are looking at the rim, those with the rim 'curving'
inwards would also be the case.
