regulatory signs such as "no entry" and “buses only" have white borders and therefore an additional white edge is not required. When these particular regulatory signs are placed on a sign with a white background the white border becomes "invisible", and the 1.5sw gap to the route symbol is measured to the edge of the red or blue part of the roundel. The effective roundel diameter in this instance is reduced to 96% of its normal size. Thus a 16sw roundel becomes 15.36sw and a 20 sw roundel becomes 19.2 sw (the red or blue part of the roundel is not increased or scaled to the nominal diameters of 16sw or 20 sw).
5.71 As with triangular warning signs, it may not always be possible to determine the length of the horizontal route arm in accordance with para 5.6. The dimensions shown will fix the minimum length of the arm. However, where the legend block has a long place name, the arm should be extended as appropriate. The horizontal position of the roundel may be adjusted in this case, provided the dimensions shown in figure 5-37 are treated as minimum values. The arm should not extend beyond the length of the legend block. Where this is likely to occur, the legend block should be moved away from the vertical route arm.
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