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For wide dual carriageway roads in flat areas, therequirements to remove water from the carriagewayare substantial,, A dual .3 lane carriageway,v/ith adjacent footway, would require gulliesat 8m spacing at a longitudinal gradient . of ;..Q.671^ _v/ith a Zfej crossfall, and this would still only limitflooding to the widths shown in .Table 1 * .In; such' \circumstances, continuous drainage by means of coveredchannels may be preferable, since these_ at the .sajnetime eliminate flowing water adjacent to footways andcentral reserves*7.3.6.5 Gullies'Suitable designs for gullies' for roads "and structuresshould be selected from Figs. 7,3-6.2 - 6, which formthe basis of the revised Highways Office standarddrawings. Fixed gully grating' should not be -used,as they choke easily and are difficult to cleanoTrapped Bullies are only necessary if the carrier drainis likely to/l|r^. For newlyconstructed roads, v/ith separate highway 'drains, it- will normally be appropriate to use untrapped gullies.Gullies in flexible pavements should be surrounded• v/ith bituminous paving material, for the reasonsgiven in pars&raph 7*3*5 , they should not be surroundedwith concrete oOn the other hand, sullies in rigid pavements shouldbe set in small, individual concrete slabs separatedfrom the main pavement slab by a butt, joint paintedwith a suitable bond-breaking substance and sealed*Transverse joints in rigid pavements should be locatedwith care so that they either join the front faceof a gully, or are. situated at least 2 metres away.;••• from the side face of any gully «7*3*6*6 Double Gully Installations • ' • • . .At lov; points in the/channel alignment, i 0 e« at asag curve, or as frequently occurs at the corners• of junctions and roundabouts, ponding vail occur inthe event of a blockage* As- a precaution, twogullies,' with a shared connection to the carrier drainphould be provided, together with kerb weirs o Theyshould be spaced at least one kerb length apart toenable the portion of Pavement between, them to beproperly constructed. .7*3*6*7 I^raijaage of .bevel and Hear Level ^oadsWhilst every, effort should be % made to. provide analignment with a minimum gradient of 0*67/^> it willoften be necessary to. accept flatter gradients,particularly in reclaimed areas * It is preferableto provide a level road, "with a drainage system/6