Traffic Signs Manual Chapter 4 Warning Signs

INTRODUCTION
12 
achieve high luminances for many drivers in defined situations, but not for all drivers in all 
circumstances.
1.13.2.  The warning signs to diagrams 501 (S2‑6‑1), 530A (S2‑4‑2), 531.1A (S2‑4‑3), 
629.2A (S3‑2‑27), 770 (S2‑2‑51), 771 (S2‑2‑52), 772 (S2‑2‑53), 779 (S2‑2‑54) and 782 
(S2‑2‑55) must be illuminated throughout the hours of darkness by internal or external lighting 
when sited within 50 metres of a street lamp which forms part of a system of street lighting 
unless within a 20 mph speed limit. In most other circumstances, reflectorisation alone will be 
satisfactory. However, some signs are sited where they will not receive adequate illumination 
from headlamps, and it might then be prudent to provide internal or external lighting regardless 
of the regulatory requirements. Examples include signs mounted unusually high above the level 
of the carriageway, or on the off side of the road. Retroreflection is also less effective where the 
sign is presented at a large angle to the direction of oncoming traffic.
1.13.3.  Illumination requirements for upright traffic signs and road markings are set out in 
regulations 8 and 9 respectively, and, where appropriate, in individual Schedules. Most warning 
signs are required to be illuminated in accordance with regulation 8. This allows a simple 
alternative between reflectorisation and internal or external lighting, although they may be lit by 
both, wherever the sign is sited. It is recommended that an assessment of required performance 
is carried out to determine the best retroreflective material for the location where a sign is 
reflectorised instead of being internally or externally lit. Materials that offer performance little 
better than conventional beaded sheetings are unlikely to be adequate.
1.13.4.  All warning signs, including those used at street works and road works must therefore 
be either reflectorised or internally or externally lit, except for the overhead black and yellow 
hazard markings and white chord markings used on railway bridges and similar structures, 
where this is optional. It is recommended that signs that are internally or externally lit are also 
reflectorised in order to maintain some degree of illumination in the event of failure of the 
lighting. Where a sign is reflectorised, all parts of the sign face not coloured black must be 
reflectorised (regulation 8). Partial reflectorisation is unlawful, as is partial lighting.

tải về 2.25 Mb.

Chia sẻ với bạn bè của bạn: