What risk existed
11The primary judge first considered whether the state of the driveway created a risk that was not insignificant (s 5B(1)(b) of the Civil Liability Act 2002) and said:
"27 Uninstructed by expert evidence I would have no difficulty in concluding that the steep surface of the driveway and the smoothness of the river stones created a significant risk of a pedestrian slipping on those stones when it was raining".
12His Honour referred in this regard to a statement of Giles JA in Gillies v Saddington [2004] NSWCA 110 to the effect that it was well open to the primary judge in that case to conclude that such a driveway "would be recognised as slippery when wet by a person going to walk upon it according to ordinary experience of life" (at [12]).
13Having referred in detail to the expert evidence, the primary judge said that the "expert evidence confirms a conclusion based on the ordinary experience of life, to which Giles JA referred in Gilles v Saddington, that the physical state of the [appellants'] premises created a risk which was not insignificant" (Judgment [55]).
14In reaching this conclusion, the primary judge had regard to Table 2 in the guide to which I have referred in [8] above. His Honour pointed out that that table related to tests conducted using the wet pendulum method which was that used by both Mr Adams and Dr Cooke. The information in the table was expressed by reference to British Pendulum Numbers ("BPNs"). The coefficient of friction of 0.51 found by Dr Cooke corresponded to a BPN of 48 and that found by Mr Adams to a BPN of 35, while his results excluding the outlier result corresponded to a BPN of 32. The table characterised the contribution of the surface to the risk of slipping when wet as "low" in respect of BPNs between 45 and 54, "moderate" in respect of BPNs between 35 and 44 and "high" in relation to BPNs between 25 and 34. From this, his Honour concluded that, based on Mr Adams' results, the driveway surface was on the cusp of having made a moderate to high contribution to the risk of slipping and, without the outlier, had made a "high" contribution to the risk of slipping.
15In written (but not in oral) submissions, the appellants criticised his Honour's use of this table as being contrary to Dr Cooke's evidence. However, his Honour was not bound to accept Dr Cooke's evidence, particularly when Dr Cooke responded to a question in the terms "so that if these cobblestones were wet there was still a moderate contribution to slipping?" by answering "[y]es to the risk of slipping that's correct" (Transcript pp 37 - 38). The process of reasoning that led his Honour to use Table 2 has not in my view been shown to be erroneous.
16Furthermore, it was open to his Honour to accept that Mr Adams' choice of testing points was more appropriate than that of Dr Cooke. As Mr Adams pointed out, the calculation of an average result for an area that varied in its slipperiness is of little value. It will be small comfort to a person who slipped on a slippery part of a surface to know that there were other parts of it that were much less slippery. Mr Adams' approach is supported by examination of the photographs in evidence which show many river stones which were smooth and rounded in appearance, and, according to common experience, therefore likely to have been slippery when wet, and many others that were more angular in appearance and more likely to have been resistant to slipping. There would be little, if any, point in deriving an average slipperiness of the two types of stones.
17In my view his Honour's conclusion that the physical state of what was undoubtedly a steep driveway created, when wet, a risk of injury to persons using it which was not insignificant has not been shown to be erroneous. As Mr Adams' evidence demonstrated, the harm that could ensue from slipping on a hard, steep surface such as the driveway might well be severe, as it was in the present case. Relevant also is that, in light of the appellants' use of the flat for the provision of accommodation to others for reward, it can be inferred that the driveway, being the only access to the flat, would have been used not infrequently by persons unfamiliar with the driveway, sometimes at night and in wet weather.