Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/161

DUAL CARRIAGEWAY ROADS

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TA 92 "Crossover and changeover design" (DMRB 8.4.6), which provides advice on changeover design, uses the concept of design speed for changeovers. This speed is directly related to the temporary mandatory speed limit of the road rather than the permanent speed limit and TA 92 gives details of this relationship. The distances given in Tables 6.5 and 6.6 are given in terms of the temporary mandatory speed limit.}}

Table 6.5 below may be used to calculate the changeover length required for roads with a permanent speed limit of 50 mph or more depending on the design speed and the number of lane changes. A smooth '5' shaped curve to suit the site conditions should be used. The lengths have been calculated from TA 92 and rounded up to the nearest 9 metres for ease of use. If a shorter changeover is required, then advice from TA 92 should be used. 160