113. We recommend a series of two signs for this purpose. The first of these (figure 40), which would be sited half a mile before the junction, is a worded rectangular sign with the legend 'Motorways merge mile' in white lettering on a blue ground. The second sign (figure 41 ), which would be sited at the junction itself, is triangular, and its inscription consists solely of a symbol in the form of a diagrammatic representation of the plan of the junction . Like the emergency signs described in paragraph 79 the sign has a white reflectorised symbol on a red non-reflectorised background with a red reflectorised border. We think the symbol is sufficiently clear to make any wording on the sign unnecessary, especially as there is a worded warning of the hazard half a mile back. The sign illustrated in figure 41 would be used on the right-hand arm of the fork and a mirror image of it on the left-hand arm; the driver will naturally identify the vertical arm of the symbol with the arm of the fork on which he is driving. For obvious reasons the sign on one arm of the fork would have to be screened from traffic on the other arm, or at least angled away from it. (The existing versions of these signs on the London-Yorkshire Motorway, in accordance with an earlier recommendation from us, do not have fish-tails in the legs of the symbol; instead there is a large arrow-head at the top of the vertical arm. We now consider that this arrow-head makes the symbol ugly and top-heavy, and that the design we now recommend is both clearer and more attractive.)
114. We have spoken in paragraph 112 of the problem of merging traffic posed by the convergence of two multi-lane carriageways. An attempt has been made at one of the forks in the first section of the London-Yorkshire Motorway, where a two-lane carriageway merges with one of three lanes, to solve this problem by separating the two lanes of the two-lane carriageway so that the fast lane merges with the three-lane carriageway some 300 yards before the slow lane. There is an island between the two lanes which is about 500 yards long but no more than eight feet wide at its widest point. The lanes and the island between them are flush and are differentiated only by means of colour, the lanes being of black asphalt and the island of concrete.
115. Clearly, if this island is to serve its purpose, and is not to be a source of confusion and danger, it must be preceded by an adequate warning sign which makes it clear that there is an island ahead and that vehicles may pass either side of it, depending only on the side of the road they happen to be on already. We have considered various forms that this sign might take; we have rejected the idea of an overhead sign with the legend 'Slow traffic-fast traffic' and arrows pointing down into the appropriate lane because we think that it might induce a sudden change of lane on the part of a driver who, being in the slow lane, fears that he may have to remain in it . We have also rejected the idea of a sign reading 'Pass either side'; to be intelligible such a sign would have to be placed on the island itself, and since the island is flush with the traffic lanes this would be dangerous. Instead we recommend the sign illustrated in figure 42. We feel that 'Don't change lane' is a clearer instruction than 'Keep in lane', which might suggest to motorists conditioned to driving on the left that they should draw to the nearside and stay there. The sign should be sited about 150 yards before the beginning of the island. It should be complemented by a single continuous white line along the middle of the carriageway extending from a point about 300 yards before the beginning of the island as far as the island itself, and the island should be made as clearly visible as possible by means of a white
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