"The duty which arises under the common law of Australia may now be considered. The authorities having statutory powers of the nature of those conferred by the [Local Government] Act upon the present respondents to design or construct roads, or to carry out works or repairs upon them, are obliged to take reasonable care that their exercise of or failure to exercise those powers does not create a foreseeable risk of harm to a class of persons (road users) which includes the plaintiff. Where the state of a roadway, whether from design, construction, works or non-repair, poses a risk to that class of persons, then, to discharge its duty of care, an authority with power to remedy the risk is obliged to take reasonable steps by the exercise of its powers within a reasonable time to address the risk. If the risk be unknown to the authority or latent and only discoverable by inspection, then to discharge its duty of care an authority having power to inspect is obliged to take reasonable steps to ascertain the existence of latent dangers which might reasonably be expected to exist. The perception of the response by the authority calls for, to adapt the statement by Mason, J. in Wyong Shire Council v. Shirt, a consideration of various matters; in particular, the magnitude of the risk and the degree of probability that it will occur, the expense, difficulty and inconvenience to the authority in taking the steps described above to alleviate the danger, and any other competing or conflicting responsibility or commitments of the authority. The duty does not extend to ensuring the safety of road users in all circumstances. In the application of principle, much thus will turn upon the facts and circumstances disclosed by the evidence in each particular case." (Emphases added and citations omitted).