119 Far from limiting the objective state of knowledge to the subjective state of knowledge of the particular builder (in the present case) or persons in comparable positions, the legislation, in my view, casts an obligation upon all persons, upon whom comparable duties are imposed, to acquaint themselves with practicable measures existing in the industry for the maintenance of safety and the avoidance of hazard. They will not be excused from a failure to perform this obligation simply because of the limits of their own subjective knowledge, except on occasions where, as Steytler J said in Hamersley Iron Pty Ltd v Robertson (Unreported, WASC, Library No 980573, 2 October 1998), it is knowledge of a special kind attributable to a specialised contractor and outside the scope of the knowledge to be expected of a builder. I must say, with all respect, that I have hesitations in limiting the scope of practicability even to that extent, because the definition of 'practicable' within s 3 of the Act speaks about 'state of knowledge' in the broad, without limiting the state of knowledge to any particular trade, profession or occupational experience. This is consistent with the policy of the Act which, in my view, is intended to achieve a situation that if, objectively speaking, there is known within an industry that there are hazards of a particular kind which may be injurious to the health and welfare of persons on worksites, and that there are means available of avoiding or reducing those hazards, then, having regard to factors such as the degree of risk, the means of removing or mitigating the risk and the availability, suitability and the cost of the means to reduce the risk, the decision about practicability will then be taken in a balanced and objective fashion.