Kent Design - Technical Appendix - Kent County Council

2.2 GEOMETRIC REQUIREMENTS FOR RESIDENTIAL
ROADS
2.2.1 TURNING FACILITIES
2.2.1.1 GENERAL
Turning facilities shall be provided wherever vehicles would otherwise
have to reverse over long distances or whenever they might turn in
locations which could cause damage to adjacent verges or footways.
Depending upon the degree of inconvenience which could be
caused, turning areas may be provided as parts of junctions.
The spacing, layout and dimensions of turning areas should be
designed to cater for the category and size of vehicle normally
expected to use them. The following criteria however, needs to be
taken into account when designing turning areas:
• Refuse and large service vehicles should not be expected
to reverse more than 40m.
• Pantechnicons should not be expected to reverse more
than 60m
• Cars and smaller service vehicles should not be expected
to reverse more than 25m
The siting of turning areas should aim to minimise the likelihood of
vehicles using them for parking. Indiscriminate parking can be
discouraged if the turning area provides direct access into the
curtilage or parking areas of adjacent dwellings. However where
casual parking is permitted outside the area required for turning,
spaces shall be located carefully between driveways as shown in fig 6.
2.2.2 GRADIENTS
2.2.2.1 GENERAL
When designing roads there is a tendency to use steep gradients to
avoid excessive cut and fill of the natural landscape. However, in
order to minimise the dangers of icy conditions and improve road
safety on bends and at junctions, there is a need to restrict the
maximum acceptable gradients. Similarly to assist in draining the road
and preventing ponding areas, there is a need to restrict the
minimum acceptable gradients.
Where changes in gradient occur, vertical curves are required at
summits and sags both for ease and comfort of driving, and at summits
in particular to ensure adequate forward visibility along the carriageway.
2.2.2.2 LONGITUDINAL GRADIENTS
The maximum and minimum longitudinal gradients for residential
roads should be restricted in line with the following recommendations.
MAXIMUM LONGITUDINAL GRADIENTS
• All vehicle, pedestrian and cycle dominated
environments, except shared surface environments
6% (1 in 16.7)
• Shared surface environments 7% (1 in 14.3)
MINIMUM LONGITUDINAL GRADIENTS
• All environments (flexible surfacing) 0.8% (1 in 125)
• All environments (block paving surfacing) 1.25% (1 in 80)
Industrial and Commercial Road gradients shall be in accordance with
section 2.3.
Shared and individual private drives shall normally have a longitudinal
gradient no steeper than of 10% (1 in 10), however access gradients
may be increased to a maximum of 12.5% (1 in 8) on sites where the
level differences make it impractical to use less steep gradients. To
avoid vehicles grounding the gradient should be maintained at 10%
(1 in 10) maximum for at least 1.5m from the back of the highway
boundary or include a roll-over detail as shown in Fig 7.
design
FIGURE 6 - CASUAL PARKING
2.2.1.2 TURNING CONFIGURATIONS
ROLL-OVER
Manoeuvring requirements can be checked by using standard
templates based on vehicle types expected to visit and use the site.
A wide variety of turning movements for various vehicle types are
given in Appendix 1 of Design Bulletin 32 ‘Residential Roads and
Footpaths - Layout Considerations’ 2nd Edition 1992.
Designers should use this data to construct the form and size of the
turning area best suited to a particular road type. The diagrams give
the minimum envelope required to contain the movement.
Nevertheless, consideration shall be give to the tolerances which
may be necessary, the layout of the road type and the possibility of
kerb overrun and how the area would be swept by mechanical
sweepers.
Manoeuvring requirements can also be checked using one of the
widely available computer software packages currently on the
market. These packages enable designers to generate sweep paths
for particular vehicle types and to superimpose them onto predrafted
layout drawings.
WIDTH WIDTH WIDTH
FIGURE 7 - GRADIENTS AND ROLL-OVER DETAILS
A G U I D E T O S U S T A I N A B L E D E V E L O P M E N T
Kent
Design
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