# Traffic Signs Manual/Chapter 4/2013/6

GENERAL
6.1 Steep hills are signed using diagrams 523.1 and 524.1 together with associated supplementary plates. The gradient is calculated using the tangent of the angle concerned, although in practice it makes little difference whether the sine or the tangent is used. The gradient on new signs must be expressed as a percentage; old signs showing a ratio may remain in place until life-expired.
DESCENT
May be used with diagram 511, 525, 526, 527, 570, 572, 573 or 817.2. The numerals may be varied (see Appendix C)
May be used with diagram 511, 525, 526, 527, 570, 572 or 573. The numerals may be varied (see Appendix C)
May be used only in combination with diagram 523.1 or 524.1
May be used only in combination with diagram 512, 512.1, 512.2, 513, 523.1, 524.1 or 554.1
May be used only in combination with diagram 523.1 or 524.1. The distance may be varied (see Appendix C)
6.4 The circumstances justifying the additional plates cannot be stated precisely. Traffic authorities, after consulting the police, will have to assess the need to advise drivers to engage a lower gear and gauge the likelihood of this instruction being respected. It is difficult to persuade drivers to select a lower gear to descend a long hill if their own assessment of the need is different. Where drivers have a good view of the descent and can make their own judgement, then an instruction to change gear will be obeyed only if ​they think it correct. Instructions should not be given it they are likely to be ignored and any existing signs which are not being respected should be removed.
6.5 "Low gear" plates are not normally used unless the gradient overall or in part exceeds 12% and the hill is longer than 800 metres. They are more likely to be justified where there are also sharp bends.
6.6 The instruction to "Keep in low gear" (diagram 526) should be used at intervals of not less than 800 metres where the gradient exceeds 12%; it may be accompanied by diagram 554.1 "Try your brakes" (see para 11.2). When used in advance of an escape lane, diagram 523.1 should be replaced by 554.1 as shown in table 6-1. Exceptionally, diagram 526 may be used at a shorter interval, e.g. where an increase of gradient is hidden from view.
6.7 "Steep hill" signs without plates may be repeated on a hill where the gradient steepens but should not be placed at intervals of less than 550 metres unless the gradient increases by 5% or more.
ESCAPE LANES
May be used only in combination with diagram 523.7 together with either 525 or 526, or diagram 554.7 with 526. The word "ahead" may be varied to a distance or to an arrow pointing to the left, or omitted. The angle of the route symbol may be varied to accord with the layout
6.9 Where an escape lane or arrester bed is available, the "Escape lane ahead" sign (817.2) should be used. It should form part of a sequence of signs with "ahead" varied as in table 6-1. The sign may also be varied to show the escape lane to the left on a straight road. Permitted variants are illustrated on the working drawings (see para 1.8). The order of the sign plates, from the top, should be: warning sign (523.1 or 554.1): supplementary plate (525 or 526): diagram 817.2.
Table 6-1 :
| Location | Warning sign | Plate | Variant of 817.2 |
| At top of hill | 523.1 | 525 | ahead |
| 400 yards from escape lane | 554.1 | 526 | 400 yds |
| 200 yards from escape lane | 523.1 | 526 | 200 yds |
| At entry to escape lane | 523.1 | 526 | arrow |
ASCENT
6.10 The sign shown in diagram 524.1 should be used only:
(i) where the gradient is 15% or more, or
(ii) where the ascent is longer than 1600 metres and the gradient is 10% or more, in which case the sign should be accompanied by a distance plate to diagram 570 (see section 18).
6.11 The supplementary plates to diagrams 525, 526 and 527 should not normally be used with the ascent warning, except in rare circumstances e.g. where a very sharp increase in gradient is hidden from view and there is a record of accidents due to vehicles stalling and rolling back out of control.
6.12 For signs to diagram 583 and 583.1 (indicating slow-moving vehicles) see paras 20.3 and 20.4.