Traffic Signs Manual Chapter 4 Warning Signs
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| 1.8 Sign sizes
1.8.1. Warning signs are normally prescribed in five sizes. The normal minimum size is indicated in the Schedule diagram by the first dimension, with alternative sizes below. All sizes are in millimetres unless stated otherwise. Signs need to be of a size appropriate to the prevailing traffic speed on the road on which they are used. On roads with a 30 mph speed limit, the smallest prescribed size of warning triangle (normally 600 mm) is usually adequate. On roads where speeds are higher, signs need to be larger. This enables them to be detected at a greater distance and ensures that drivers have sufficient time to recognise and assimilate the warning and take any necessary action before the hazard is met. The largest signs are for use on motorways or high‑speed roads. Appendix A details the appropriate size of sign for various speed ranges, based on the 85th percentile approach speed. 1.8.2. Where special amenity considerations apply, or there are physical constraints on the width of sign that can be accommodated, the next smaller size can be substituted. It should however be borne in mind that smaller signs are likely to be seen later, and do not become legible until drivers are closer to them, giving less time to react. 1.8.3. If the accident record suggests that drivers are failing to notice the warning, or seeing it too late to take the necessary action, the next larger size can be used. Conspicuity can also be increased by the use of yellow backing boards (see tải về 2.25 Mb. Chia sẻ với bạn bè của bạn:
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