In Unger v. Shire of Eltham[81] a road authority was held liable for damage sustained through a hole in a broken culvert over a drain across a country road. There was no negligence in the original construction, but the jury found negligence in allowing the culvert to become rotten and unfit for traffic, and in allowing the hole to remain in the culvert without repair and without giving notice to persons using the road. The ground upon which the court held the defendant shire liable was that it had made a drain across the highway which, unless covered, would be a nuisance and a duty was thus imposed upon it to maintain the covering. The question was decided upon a special case which contained no statement of the nature or purpose of the drain, but it may be suspected that its sole purpose was to carry off surface water from the inner guttering of a hillside road, and that it formed an ordinary incident in the construction of a mountain road. If this were so, the decision was, in my opinion, incorrect. On the other hand, if the defendant had made the drain, not as road authority but for some other purpose, as, for instance, a drainage scheme foreign to road construction, the decision might be supported. It is a mistake to suppose that simply because a thing such as a covered drain or gutter is of such a nature that it will, when it falls into disrepair or dilapidation, cause a dangerous condition of the highway, it is incumbent on the road authority which put it there to take active measures to prevent or remove that condition. If the drain or gutter forms part of the road construction and is put there to serve a purpose arising out of its character as a highway, as for example to carry off the surface water, or to drain off seepage and protect the road base, the road authority incurs no civil responsibility by allowing it to fall into a condition of danger, unless in the first instance it acted improperly in placing it there. If the road authority showed a want of care or skill or took an unreasonable??? in the adoption of such an expedient or in the design or execution of the work, neither lapse of time nor the use in the interval of some additional precaution which while it was practised had prevented any ill consequences ensuing would relieve the road authority of civil responsibility for damage ultimately caused by the work. But, given due care and skill and proper regard for the public safety in the first instance, the road authority does not lose its immunity from liability for damage arising from its failure to uphold, maintain and repair because the work that it has done for highway purposes may, or even probably will, under the influence of wear and tear and the stresses of use, give rise to a defective or dangerous condition. To speak of the resulting state of the road as a nuisance in the highway may be correct enough. There is, of course, always a risk in applying the word to the physical thing instead of to the act or omission constituting the wrong of nuisance. But, apart from that, the question is not whether a nuisance has been caused. A highway authority might be indictable for a nuisance arising from its failure to repair. But it was not liable for the particular damage which an individual suffered from the indictable nuisance. When the highway authority acts in that capacity the question is whether, by the negligent exercise of its statutory powers or otherwise without statutory justification, it has been the active agency in causing the nuisance. It is for this reason that I expressed the view that it was of little importance in the present case whether the road at the time of the accident should be considered as still under construction or as under repair by the Minister. For, on the one hand, if the drain had been put in Garratt Road, not for road purposes, but for some foreign purpose, as, for example, if it had been a sewer, it would remain under the control and responsibility of the authority which put it there whether road board or some other authority and would not be part of the subject matter which the Minister might construct or repair under sec. 86 (1) of the Public Works Act 1902-1933 W.A. considered alone. On the other hand, if the drain formed part of the road construction undertaken for road purposes, the road board's liability depends upon the propriety of its original act, and the subsequent failure to repair amounts only to a step in causation. To whichever authority the care of the road belonged for the time being, the result would be the same. The causation would be complete.