• Style & appearance
• Product data
• Design considerations
• Installation & Maintenance

Style & appearance

Photographs

Product photograph

Accessory units
Highway Shallow Base Unit (for use in areas with restricted depth)	Deep Base Unit (for extra capacity)
Base Unit with concrete drainage top	Crossing Base Unit (galvanised steel plate)
Silt Box Top / Cover 01460 (ductile iron)	External Radius Unit Also available: internal radius (dotted)
Junction Unit (two units form junction)	Combined Outlet Junction Unit
Outlet Units (two units form outlet)	Cable Duct Unit
Base Unit with Ductile Iron Grid 01604 (Class D400 and E600)

Product data

Trafficking

• Highways
• Commercial sites
• Industrial sites
• Access roads

Features and benefits

• Integrated kerb and high capacity linear drainage system
• Dramatically reduces the need for expensive underground piping and cost of excavation
• Requires only simple kerb-laying installation (no added underground pipework)
• Multiple inlet holes along the length of kerb remove water immediately from the road surface
• Large capacity channel stores and removes water to an outlet, removing the need for frequently placed gully grates
• Cost effective compared to other combined kerb and drain systems
• Supplied in pallet packs for easy maneuverability on site
• Packed to suit manual handling

Main units dimensions

Available from stock and supplied in pallet packs: (base) 16 units and (top) 8 units
Channel dimensions 300x300 mm (approx.)
Inlet dimensions 65 x 150 mm ellipse (approx.).

Accessory units dimensions

Radius units: 25/11, 10/8, 7/6 metre versions, for external radii.
Radius half units available for internal radii in same sizes.

Design considerations

Description

A drainage system with multiple inlet holes along full kerb length, available in both half batter and splay profiles. The U-shaped channel has a cast-in recess for sealing mastic.

Composition and manufacture

Highway is manufactured from high quality granites and quartzite using both wet pressed and semi dry processes.

Complementary products

British Standard Kerb.

Loading standards

Conforms to EN 1433 Class D. (Class D=400kN: Public highways and general parking areas).

Performance

Strength

Meets requirements of BS EN 1433.

Specification clauses

Assistance with model specification clauses is available for this product,
please refer to Charcon Technical Services.

Colour availability

Standard

Basic components

Two-part kerb comprising:

• Base unit: high capacity channel.
• Top unit: soffit for channel – incorporating semi-elliptical inlets.
• Splay and Half Battered options available.

General Principles

The aim is to ensure prompt and cost-effective removal of surface water during and immediately after rainfall.
Multiple inlet holes and the continuous U-shaped channel profile enable system design which minimises underground pipework. This can provide a lower-cost solution than traditional gully systems.

System capacity

For Highway drainage, identify any flow constraints in advance, including:

• vehicular crossings requiring crossing base units
• tight radii*
• junction units creating turbulent flow*
• outlet unit capacity
• outfall chamber/pipe capacity
• linear grates

Note:
*Hydraulic properties given in tables are conservative and so, in most cases, any flow reductions arising from these factors may be ignored in design.

In common with all combined kerb and drainage systems, Highway top and base units will NOT run full due to turbulence from the inlet holes. System flow capacities, given in the table below, are therefore confined to realistic flow levels rather than theoretical/full bore maximum levels.
Capacities vary according to type of base unit installed in the system, (standard, shallow, deep or crossing base units – see table below).

Note
Capacity will be reduced over time wherever there is a likelihood of a significant build-up of silt.

Highway system flow capacities

Key: Vel. = velocity, dis. = discharge

Inlet capacity

The capacity of each inlet, maximised when first laid, can be affected by future re-surfacing which may raise carriageway levels above the normal 125 mm kerb-face. If so, capacity can be protected by cutting back the surfacing adjacent to each inlet (special tool available).

Outlet capacity

In practice, capacity requirements can vary according to location of the outlet and the depth of flow within the system. For design purposes, an outlet capacity of 62 mitres per second should be adopted. If this capacity is insufficient, more than one outlet unit should be installed to discharge into the outfall chamber.

Outfall chamber/pipe capacity

Outfall discharge capacity should be as large as possible to ensure benefits from Highway system. In large schemes, gully pots used as outfall chambers may be insufficient because turbulence can reduce capacity levels below that which a standard 150 mm outfall pipe can sustain. Where possible, purpose-built chambers (brick or precast manhole rings) are recommended instead to help minimise effects of turbulence on capacity. The appropriate outfall pipe can then be selected to suit the specific case (see table below).

Linear grates Highway can be used for long runs of linear drainage where high volumes of surface water drainage is required or high wheel loads are imposed.

Highway outfall pipe capacity

Installation design – units

General principles

All units are unreinforced: protect from stresses caused by thermal expansion of cementitious paving materials. Leave 1mm gap between each unit to prevent damage from thermal expansion of the units themselves.

Expansion joints MUST be installed on each side of drainage runs in concrete pavements or those incorporating a cement bound/lean mix concrete roadbase.

DO NOT place these joints directly adjacent to any trafficked unit as this would allow units to rock under trafficking and may allow water ingress into the base or sub-grade.

• Recommended position of joints (minimum distances):
• 600 mm from Clearway/Safeticurb units (see Figs 12-14).
• 125 mm from Highway units (see Figs 5-6).

Note:
As Highway units are not regularly trafficked, expansion joints could be placed directly against them. However, 125 mm distance is recommended to avoid ingress of water between the unit and carriageway construction.

Base foundations

Recommended typical foundations are:

• for Clearway/Safeticurb: minimum 150 mm depth of ST4 concrete with a 25 mm bed of Class 1 mortar (1:3 cement: sand) to allow easy adjustment of units to line and level.
• for Highway: minimum 75 mm of concrete.

Note:
Strength, overall depth and width of the base may need to be increased when laid on low - strength sub-grades.

Haunching

Recommended typical haunches (to within 100 mm of top unit) are:

• For Clearway/Safeticurb: ST4 concrete.
• For Highway: ST1 concrete minimum 125 mm width.

General principles

Details of outlet units an inspection access differ according to which linear drainage system is used.
In any system, silt or detritus should normally be prevented from entering the main drainage sewer. An outfall chamber is required to enable silt collection before onward connection to a sewer.

Types of outfall chamber

• trapped precast concrete, clay or plastic gully pots. Gully pot capacity may be insufficient for some largerlinear drainage installations.
• Purpose-built brick or concrete inspection chamber.
• Precast concrete manhole rings.
• Dedicated sump unit.

Select outfall pipe diameter/gradient

Care should be taken to ensure sufficient capacity.

Highway

Standard outlet formed using two base outlet units (in place of standard base units) to give full width rectangular outlet 400x275 mm. (shallow and deep base outlet units available). Positioning is not critical, but should allow access for suction pipe from gully emptier.

Discharge capacity may be increased by installing more than one pair of Base Outlet units discharging into the same outfall chamber.
For larger schemes, chambers to be detailed in accordance with The Specification for Highway works, clauses 507 and 508. For larger outfall pipes it may be necessary to incorporate a manhole access at rear of run.

Clearway/Safeticurb

Select outfall chamber, pipe dimension and pipe gradient to suit system capacity. Position a silt box top on two courses of engineering brickwork over the selected outfall chamber/silt trap to give access (via the silt box lid) for silt removal.

HydroKerb sump unit

With hinged, removable lid for inspection access, is placed over sump unit in place of standard top units. (See page 143 for alternative option).

Mini Highway sump unit

With hinged, removable lid for inspection access, is placed over inflow unit in place of standard top units.

Radii

Highway/Mini Highway:

• To form external radii of 25 metres or less (minimum 6 m), special radius units should be used (see table below). As these do not cover all individual radius dimensions, some slight gaps are required between units as indicated in Highway radii gap widths table, below.
• For external radii greater than 25 metres, lay straight units with open joints.
• To form internal radii (minimum 6 metres), use 7/6 internal radius units.

Clearway/Safeticurb:

• Where necessary, standard (straight) units may be laid to form radii or bends.
• Safeticurb units: alignment ring within bore acts as a former for infill mortars to seal joint.

Crossings

Highway/Mini Highway:

• Use crossing base units to carry drainage runs under side roads/vehicular crossing points. Grid units available.

Safeticurb (DBK unit only):

• To continue linear drainage at road junctions, kerb crossing points (pedestrian/vehicular), use transition units to reduce kerb height to road level. These connect with standard grid or slot units as necessary.

Junctions/sharp bends

Clearway/Safeticurb:

• Use silt box top at outlets or with suitable uPVC pipe fittings (cut to fit) to form junctions or sharp bends.

Highway radii gaps widths