in the darker green that would need to be set against their preference for it on amenity grounds. In their opinion it had, when surrounded by the white border proposed, adequate target value both in urban and rural settings, was a more pleasing colour in itself and would be more readily distinguishable from the greens commonly used on shop-fronts, advertisements, vehicles and the like. By providing a greater contrast in tone it also , they thought, made the message carried by the sign easier to read.
The majority of us, however, were firmly of the opinion that this shade of green was too dark to be distinguishable from black in failing daylight and during the many dark days which occur in a British winter. It did not show up sufficiently clearly as green, if at all, under external illumination. Finally the improved contrast with white lettering claimed for the darker green was not shown by experiment to be significant.
141. The basis for our selection of the forms of lettering illustrated at figures 1 , 2, 4 and 5 is set out in paragraphs 40 to 44. The wording on directional signs should invariably be in lower-case lettering with initial capitals and the route letters in upper-case.
Letter height, together with sign layout and positioning, is an important factor in ensuring that the necessary information is conveyed to drivers clearly and in good time for them to slow down or make any appropriate manoeuvre. Letter sizes for directional signs will depend on vehicle speeds at the site of the sign and the distance of the sign from the driver's path. Following the principles upon which calculations were made to determine the letter height for directional signs on motorways and dividing all-purpose roads into four groups according to vehicle speeds and carriageway widths, we recommend that letter heights for directional signs be as set out in Appendix V.
We recommend a difference of two inches in the height of the letters used in each group. This is a convenient interval and it would be impracticable for the purpose of making Ministerial Directions, or indeed for the production of signs, to have numerous variations of letter size to accord with local variations in vehicle speed. Nevertheless, the letter size of directional signs should vary with vehicle speeds on the same road. For instance, when a Primary route passes through a speed restricted town the signs in the speed restricted area should have a correspondingly reduced letter size.
We also think it convenient and appropriate that the letter height for direction and route confirmatory signs should in all groups be two inches less than that on advance direction signs, except in the fourth group.
142. We recommend that all the names on a directional sign be in lettering of the same size and that no reduction be made for places of minor importance. This will assist in making the whole sign readable at the same distance. In our view, reduced letter sizes should be used only for long place names which cannot be abbreviated or hyphenated and would otherwise require a sign wider than is consistent with good design or the space available.
143. We recommend that on all white on green Primary route signs route numbers should be yellow and that on all directional signs their height be equal
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