Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/162



Table 6.6 below uses the same calculation with the measurements rounded to the nearest 6m for ease of use on roads with a permanent speed limit of less than 50 mph. A straight "taper" layout or smooth '5' shaped curve to suit site conditions should be used.

On motorways and dual carriageway roads, the provision of a site access lane may be required on major reconstruction works, see paragraph D3.2.15 and Figure 3.2. This access lane should be a minimum of 3 m in width to allow access by HGVs etc.

The designer should note that, where a site access lane is to be provided, the police may require this lane to be used by general traffic in the event of an accident blocking the running lanes. Where a site access lane is not being provided, or is not continuous throughout the works site, the designer must ensure that the design makes suitable provision for access through the works area for use in an emergency. In a full contra-flow where the primary carriageway is closed and all traffic is transferred to the secondary carriageway, it is essential that a continuous, well-defined and unobstructed route through the site will be available for use at all times by emergency vehicles. Emergency route proposals need to be discussed early in the design with the emergency services, see Section D2.6.

The recommended lengths of lead-in tapers and the number of cones required in the tapers are set out in Table A1.3 (Appendix 1). Exit tapers, where provided, should be at 45° to the edge of the road.

The initial taper at lane closures will normally impose a merge-to-the-left manoeuvre even if traffic has to be switched subsequently to the right. A merge-to-the-right manoeuvre will normally only be permitted on works for which a relaxation applies (see Section D1.6) when: 161
 * lane 1 of a three or more lane dual carriageway road is being closed, or
 * lanes 1 and 2 of a three or more lane dual carriageway road are being closed where the road is lightly trafficked, or
 * lane 1 of a two-lane dual carriageway road is being closed where the road is lightly trafficked.