Double white lines should not, however, be used to prevent overtaking on the approach to roundabouts, pedestrian crossings or road junctions.
Suggestions have been made that double white lines should be laid so as to allocate the centre lane of straight and level three-lane roads alternately to opposite streams of traffic. Our prima facie view is that the use of double white lines in these circumstances would jeopardise their observance elsewhere, but we appreciate that, with rapidly growing traffic, Departments may wish to try out every possible means of increasing safety on straight three-lane roads, including the use of offset double white lines on alternate lengths. The use of offset double white lines in such a way as to permit alternate overtaking by opposing traffic streams on winding three-lane roads might reasonably be permitted if the experiments now being undertaken clearly demonstrate it to be both safe and advantageous.
227. The markings prescribed (Regs. RM 3 and RM 20) are intended to warn drivers on the approach to a hazard such as a road junction or a bend not to cross the line unless they can see that it is safe to do so. We have some doubts about the effectiveness of the present form of this marking and think that a more emphatic broken line would be better and we recommend that trials be carried out to determine how best this additional emphasis should be given.
Warning lines on the approaches to junctions and other hazards should more frequently be extended beyond the minimum length at present recom mended.
We consider the markings now prescribed (Regs. RM 19) to be generally satisfactory though we think that on fast all-purpose roads these markings should be more emphatic and approximate more nearly to those in use on motorways.
229. The new transverse broken line marking which we have recommended will serve to mark the edge of the main carriageway at those places where it is used on side roads.
The single broken line marking (Regs. RM 6) will continue to be required, however, to serve its prescribed function of marking the edge of the carriageway where this is in doubt, for example, at lay-bys. It could also be usefully employed, for example, where a minor road joins a major one at a widely splayed Y junction. Under such conditions the left half of the mouth of the minor road would be marked with the recommended new marking and the remainder with the single broken line, thus forming a continuous guide line to help drivers on the major road by night, and particularly in fog, to follow the course of the road. Here again we feel that a more emphatic form of edge of carriageway marking is needed on high speed roads.
230. The marking prescribed at Regs. RM 24 is for use in connection with a restriction on loading and unloading. We have referred to it in paragraph 87 (ii) as part of our recommendations on waiting restriction signs.
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