The height shown on the sign must be to only one decimal place. Sign the bridge with the remaining whole number and first decimal digit, as reduced,Į.g. (ii) if the second decimal digit is 7 or less, delete it and reduce the first decimal digit by 1. (i) if the second decimal digit is 8 or 9, delete it and sign the bridge with the remaining whole number and the first decimal digit, The following method is then used to calculate the appropriate signed height: Thus, the maximum headroom that will normally appear on a sign is 16-0".ħ.12 To obtain the metric figure shown on signs, the bridge height should be measured to two decimal places, rounding down to the nearest 0.01 m. If the resulting figure is not a multiple of 3 inches, it should be rounded down to the nearest lower multiple of 3 inches.Įxample 1: measured height 15'-2 subtract 3" to create a safety margin 14'-11 round down to nearest multiple of 3" and sign as 14'-9".Įxample 2: measured height 14'-6, subtract 3" to create a safety margin 14'-3 and sign as 14'-3" (rounding down not required as already expressed to the nearest 3") Where the road passing under a structure is on a sag curve, the headroom should be measured along the carriageway over a 25 m chord.ħ.11 The imperial figure shown on signs to indicate the available headroom should be at least 3 inches less than the measured height to allow a safety margin. the effective clearance will be reduced for a long wheel base vehicle spanning a dip. Changes in gradient might affect the headroom, e.g.
This is particularly important where the road dips or hogs sharply or is on a curving alignment under the bridge. 7.10 Care should be taken to ensure that vehicles of the maximum length permitted by the Construction and Use Regulations will be able to pass safely under the bridge. Imperial and metric heights should be calculated separately. Metric signs alone must not be used either two signs or a combined metric/imperial sign must be used. It is strongly recommended that both units are displayed on signs, especially on main routes and roads used frequently by foreign vehicles. The Regulations allow heights to be shown in either imperial units or both metric and imperial units. Where a dual carriageway road has hard shoulders with restricted headroom, this should be separately signed, supplemented with the hazard markings in diagram 530.2 or the chord markings used at arch bridges (see paras 7.23 and 7.24).ħ.8 All bridges and other structures with a headroom of less than 16'-6" (5.03 m) should be clearly signed. Where the clearance over any part is less than this, signs should be provided. However, fluorescence is visually intrusive and is therefore best confined to structures that are known to be at risk.ħ.7 The standard minimum clearance over every part of the carriageway of a public road is 16'-6" (5.03 m). The latter greatly increases conspicuity in dull weather and at dusk (see para 1.33 for further guidance on fluorescence). The yellow parts of these markings may also be reflectorised, making them much brighter at night, and fluorescent. The use of black and yellow hazard markings helps to make the vulnerable parts of a structure more conspicuous. It is therefore particularly important that the signs and markings on low bridges are correctly installed and maintained to a high standard. Serious damage can also be caused to arch bridges.
It takes only a relatively small amount of force to displace bridge girders sufficiently to derail a train. There is a significant number of reported bridge strikes each year. LOW BRIDGES 7.6 Incidents in which road vehicles strike low bridges present a serious hazard to both rail and road users. The Regulations permit the use of yellow material which is both retroreflective and fluorescent (see para 7.6). The signs should be used as in the diagram, sloping downwards towards the carriageway.
If the obstruction is accompanied by a narrowing of the carriageway, "road narrows" signs to diagram 516 or 517 (see section 4) and edge lines should also be used. The use of these signs helps to make the vulnerable parts of a structure more conspicuous. It is therefore particularly important that signs to diagram 528.1 on parapets or abutments of bridges are correctly installed and maintained to a high standard. In addition to the risk to passing road traffic, damage to a parapet can also result in considerable danger to rail traffic.
#Underpass ahead sign drivers#
This includes any parapet or abutment on the off side where it would be a hazard to drivers overtaking or passing a temporary obstruction on the near side. 528.1 End of bridge parapet or other obstruction 7.2 Signs to diagram 528.1 should be used where a bridge parapet, abutment or other obstruction is immediately adjacent to, or encroaches onto, the carriageway.
0 kommentar(er)
