periods, the interval between applications to be as short as possible. A record has to be kept of the amount of deformation during each loading and of the percentage of recovery. If the recovery is less than 50% after the third application offeree, the barrier has failed the test. If recovery is between 50% and 75%, there must be a re-test. The question is: 50% or 75% of what? Is the recovery to be in relation to the position of the barrier before the first application offeree or before the third? If the former, a span of 124a recorded 53% at the 1988 test and should have been re-tested. If the latter, it recorded 100% and passed. Unfortunately the Green Guide is unclear as to the correct interpretation. Dr Eastwood took the latter view and so passed the barrier. He justified his interpretation in evidence. He said failure to recover to the original position could be due to a "shake-down" effect related to some giving in the ashes under the concrete or to some other extraneous factor rather than to any defect in the material of the barrier itself.
239. I think, after consulting Professor Maunder, that safety ought to have dictated recovery should be by reference to the position of the barrier before the first application of force. I accept, however, that the Green Guide is ambiguous and Dr Eastwood's interpretation is tenable. It has some support from the British Standards tests on steel structures. Clearly, however, for the future, the Green Guide should be clarified on this point.
Corrosion
240. Inspection of barrier 124a, and indeed other barriers at Hillsborough, by the HSE showed considerable corrosion of the metal at vulnerable points where water could accumulate. Dr Eastwood agreed that if a significant degree of corrosion was observed on visual inspection, a barrier should be condemned.
241. The Green Guide does not specifically refer to corrosion. Paragraph 39 provides, inter alia:
"Crush barriers and balustrades should be examined for deformation or any other overt signs of weakness".
Paragraph 6 of Annex C provides:
"If during any test, even though the barrier... satisfies the above loading requirements, doubt should arise for any reason (including such matters as cracking of the terracing or distortion of connections) as to the safety of the barrier... a detailed investigation should be carried out. Unless the results of this investigation remove the doubt as to safety of the barrier... (it) should be deemed to have failed the test".
242. Since corrosion is a likely cause of deterioration, a revision of the Green Guide should make specific reference to it.
Causation
243. Tests done by the HSE suggest that although barrier 124a passed the loading test in 1988 and probably would have been able to sustain a force which did not exceed the test load, it was unable to resist the load imposed upon it by reason of the numbers in pen 3, the excessive gap in the barrier higher up the pen and the absence of barrier 144. Corrosion probably played a part, but the effective cause of the collapse was the excessive and unanticipated pressure to which the barrier was exposed.
