the centreline of the front axle and the centreline of a virtual axle equally distant from the second and third axle in the case of a three axle vehicle.
lárlíne an acastóra tosaigh agus lárlíne acastóra fhíorúil atá ar comhfhad ón dara agus ón tríú acastóir i gcás feithicil trí acastóir.