B4.5.2 Vertical alignment

Development proposals must ensure that:

• the maximum longitudinal gradient for all adoptable streets does not exceed 1 in 20 (5%)

• there are no proposed street gradients steeper than 1 in 12 (8.5%), under any circumstances

• on the non-priority approach to a junction, the carriageway gradient is no steeper than 1 in 40 (2.5%) for the first 10 metres, with an absolute maximum of 1 in 25 (4%) thereafter

• where carriageway gradients exceed 1 in 20 (5%), a separate pedestrian route is provided that is designed with gradients that are safe, accessible, and compliant with relevant standards

• at pedestrian crossing points and vehicle crossings, the level difference between the dropped kerbs and full-height kerbs on the uphill side must be reduced over two transition kerb lengths.

• to enable adequate drainage, all paved areas must have a minimum gradient of 1 in 50 (2%)

The lowest point of any adoptable carriageway must be 0.6 metres above the 1 in 100 year flood level.

A minimum vertical clearance of 5.3 metres must be provided across the full carriageway width, with an additional 0.45 metre clearance on either side.

Exception: For Local Residential, Shared Surface or Private Drives accessed via an archway, a reduced minimum vertical clearance of 4.2 metres may be permitted, subject to appropriate design justification.

When designing streets, applicants should, where possible, follow the natural topography of the site to avoid creating an unnatural or overly engineered appearance. For acceptable longitudinal section gradients and crossfalls, please refer to the Street Hierarchy (List 3).

Carriageway crossfalls should be 1 in 40 (2.5%) from the high side to the centreline and 1 in 25 (4%) from the centreline to the low side to reduce the visual impact of the crossfalls, unless an alternative acceptable solution is proposed.