4. The Minister has authorised the use on roads of engineering plant notwithstanding that such vehicles do not comply in all respects with the requirements of the Rules, subject to the conditions and restrictions in paragraphs 6 and 7 and also to the following conditions and restrictions:(a) | every such vehicle shall be so constructed that it is either a wheeled vehicle or a track laying vehicle; | (b) | in the case of a wheeled motor vehicle rules 10, 16, 18(1), 24, 25, 30, 33, 34, 96, 99, 101, 104, 105, 106, 107, 109, 110, 111, 114 and 115 of the Rules shall apply; | (c) | in the case of a wheeled trailer rules 10, 96, 99, 104, 105 and 109 of the Rules shall apply; | (d) | in the case of a track laying motor vehicle rules 10, 16, 18(1), 24, 33, 34, 96, 99, 101, 104, 105, 114 and 115 of the Rules shall apply; | (e) | in the case of a track laying trailer rules 10, 96, 99, 104, 105 and 109 of the Rules shall apply; | (f) | all wheels of any such vehicle which are not fitted with pneumatic tyres or tyres of soft or elastic material shall be smooth and have the edge rounded to a radius of not less than 12 mm. and not more than 25 mm.; | (g) | the total weight transmitted to the road surface by any wheels not fitted with pneumatic tyres of any such vehicle in line transversely shall be such that the average weight per 25 mm. width of tyre in contact with the road surface shall not exceed 30 kilograms; | (h) | every track laying vehicle shall be so constructed that —(i) | the parts of the track which come into contact with the road surface are flat and have a minimum width of 12 mm.; and | (ii) | except in the case of a track laying road roller, the total area of each track actually in contact with the road surface at any one time is not less than 0.023 square metre in respect of each tonne of the total weight of the vehicle which is transmitted to the road surface by means of the tracks; |
| (i) | in the case of a motor vehicle which is not propelled by a reversible steam engine, an efficient brake shall be fitted, and such brake shall at all times while the vehicle is used on a road be maintained in good and efficient working order and shall be properly adjusted; and | (j) | in the case of a trailer which is not drawn by a locomotive, suitable scotches or other similar devices shall be provided so designed and constructed as to hold the vehicle stationary when necessary, unless an efficient brake is fitted. |
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