Kerbing and Channel Block Implementation
1.1 Kerbs are used to delineate and support the edge of a footway or off-road cycleway . They also support the edge of the footway/cycleway/carriageway.
1.2 Channels provide a route for water to drain to gullies and are normally used to facilitate drainage of surface water in areas where there is little fall .
2.1 Kerbing (general)
Where kerbing is used, full height kerb upstands will generally be 100mm except where existing constraints dictate otherwise or on bridge decks where 75mm will normally be used..
Unless otherwise noted below the general presumption on new works is that Full Batter/Splayed (Standard detail /C/010 Type PC2 Splayed kerb SP) kerbs should only be used where there it is anticipated that vehicles will over-run them and any adjacent footway should be set back by at least 3.0m - or protected positively - in some way to ensure it is not over-run.
‘Dropped kerbs’ where a vehicular access crosses a footway or verge will normally have a 25mm upstand. Where a pedestrian crossing crosses a footway or verge kerbs shall be laid flush with the carriageway. Unless specified elsewhere for flush kerbs square channels laid on edge shall be used.
ST1 concrete will normally be sufficient for backing and bedding to kerbs but in industrial areas or where kerbs are likely to be over-ridden by commercial vehicles ST4 concrete should be used.
Kerb units are heavy items so in the majority of cases the use of suitable lifting aids will be required. A site specific risk assessment should be carried out and recommendations implemented prior to work commencing.
The Code of Practice for Laying Natural Stone, Precast Concrete and Clay Kerb Units, BS 7533-6, shall be followed unless the appropriate HCC Standard Detail instructs otherwise.
2.2 Kerbing in Totally Rural Areas
These are typically roads which have grass verges bordered by hedgerows, fields and woodland where no footway exists.
The County Council as the Highway Authority has a general presumption against kerbing in rural areas unless it is to prevent overrunning, or to assist drainage, or within villages. However, where engineering factors deem kerbing to be necessary the ‘County Traditional’ (CT) type kerbs shall be used. Where such kerbing is used to prevent over-running on bends or at junctions the kerbing should normally be laid on end to a 15 degree batter to help reduce possible tyre damage. Where over-running is acceptable (i.e. no footway within 3.0m) a 45 degree batter should be used.
2.3 Kerbing Urban Areas
The County Council as the Highway Authority has a general presumption towards the use of hydraulically pressed concrete (PC) kerbs complying with BS EN 1340 . Half batter kerbs (HB2) should normally be used where there is a footway adjacent to or within 3.0m of the carriageway. 45 degree splay kerbs (SP) may be used where there is no footway within the verge (see Standard Detail/C/010A). Where it is considered desirable to moderate the appearance of the kerbing an exposed aggregate Countryside Classic kerb may be used (see Standard detail/C/020A)
2.4 Kerbing in Special Urban Areas
‘Special Urban Areas’ are typically roads in towns, villages and other built up areas where consideration needs to be given to the use of special materials to blend sympathetically with the environment and where the existing kerbing may be in natural stone.
The County Council as the Highway Authority has a general presumption that in special areas consideration shall be given to the use of natural and special materials to blend sympathetically with the environment. Specific advice may be gained from the Environment Department’s Landscape Planning team.
Wherever possible existing natural stone kerbs should be reused with matching new or reclaimed natural stone kerbs used to make up any shortfall if insufficient nos. are suitable for reuse.
Where natural stone kerbs are not an option, for whatever reason, then ‘Conservation’ (CO) type kerbs should be used (see Standard Detail/C/025A)
2.5 Kerbing in Semi-Rural Areas
Typically roads in hamlets and on the fringes of villages and towns where there is normally a mixture of grass verges and footways
Where there is a need for kerbing careful judgement will be needed in deciding on the type to be used. Precast Concrete kerbs may be appropriate if they match what has been used in the area. Alternatively County Traditional (CT) kerbs as noted in 2.2 may be used.
2.6 Kerbing in ‘industrial’ Areas
In industrial areas the County Council as the Highway Authority has a general presumption towards the use of ‘Precast Concrete (PC) kerbs with stronger bedding and for combined kerb/drainage units. The dedicated Standard Detail/C/125B for these exist and should be used wherever feasible.
2.7 Kerbing for cycle paths
For a cycle path in an urban area with a greater than 30 mph speed limit there is a requirement for a min. 500 mm demarcated separation strip behind the kerb face
2.8 Bus Access Kerbs
Where bus access kerbs are installed in order to reduce the step height between the footway and bus platform a160mm upstand should be achieved to avoid grounding of the front overhang on the bus. ‘Kassel kerbs’ and ‘Access kerbs’ are two suitable products for use in such situation. The dedicated Standard Detail/C/035B or /C/040B for existing footways should be used wherever feasible
2.9 Heavy duty Safety kerbs
These are marketed under the names ‘Trief kerbs’, ‘HGV Kerbs’ & ‘Titan kerbs’. They differ in terms of profile, overall dimensions and available accessories so careful consideration should be given in choosing the appropriate product in each instance. They are primarily aimed at preventing large vehicles over-riding them and as such they are substantial in terms of size and hence their appearance, size and cost is likely to mean usage will be limited in Hampshire.
2.10 Kerbing on traffic calming schemes
When designing kerb build-outs for traffic calming works, etc the leading kerb face should be angled at 45 degrees to the direction of traffic to minimise the potential for damage in the event that a vehicle should strike the build-out. More importantly, when detailing the exposed corner of any build-out, it is essential that a minimum radius of 300mm should be incorporated to avoid damage to wheels and tyres. Great care should be taken in cutting and shaping kerbs in this area to avoid sharp edges and quadrants should be employed where necessary.
2.11 Combined Kerb and Drainage Units
There are several manufacturers of this type of unit each differing to some extent from the others, some come as two parts. Hampshire County Council has a general presumption against the use of these systems. However, these units may be used to provide drainage where there is little or no longitudinal fall or where providing conventional piped drainage would be exceptionally difficult or impossible. The choice will be governed by the site circumstances and the relative costs. In choosing the product consider the need for necessary maintenance and ensure there are sufficient rodding access points. An access point should be provided at each transition to a dropped crossing to facilitate cleaning. Water jetting can be rendered ineffective when water escapes from the side apertures. It may be necessary to block these temporarily during cleaning. It is not recommended to site these systems in an area where there will be a build up of leaf or other litter as this can block the apertures or the water channel necessitating frequent cleaning. Should they be used where there is a good longitudinal fall sufficient transverse fall must also be provided to ensure water enters the side apertures and does not flow past. Installation should be in accordance with the manufacturers recommendations. It is not recommended to use two part systems adjacent to block paved carriageways as it is considered not to provide sufficient support to the kerb face section of the unit.
3. Channel Blocks
The County Council as the Highway Authority has a general presumption against the use of channel blocks. Where channel blocks are deemed necessary they shall be limited to troughs or crests in the vertical road alignment where the gradient is between 0.8% and 0.5%. Channel blocks shall conform to BS EN 1340 and the performance classes as for kerbs above.
Version No: 1.1
Effective from: 14/10/2010
If copied or printed, this document should be treated as uncontrolled and correct only at the date it was copied or printed.