Highway Slope Manual

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ighways are environments with a strong functional characteristic and the aesthetic
treatment of slopes should ensure that the normal functioning of the highway is not in any
way impeded. In particular, the functional clearances of roadside features should meet
minimum standards, as should features that define sight lines. eference should be made to
the Transport Planning and Design anual olume 2 Chapter 3 (Transport Department, 198.)
on visibility and sight-line standards.
Designers should note that various Government Departments have set up etting
Committees on Slope Appearance to control the use of sprayed concrete in slope works (Works
Bureau, 2000). Also, the aesthetic design of retaining structures associated with the public
highway system should be submitted to the Advisory Committee on the Appearance of Bridges
and Associated Structures (ACABAS) for their vetting (Works Bureau, 1998b and 1998c).
6.4 AINTENANCE CONSIDERATIONS
aintenance responsibilities in and around the highway environment may involve
maintenance parties from a number of different Government Departments. When designing
roadside slopes, the designers should take note of the maintenance parties for the completed
landscape works by referring to Works Branch (199.a) and should ideally consult these
parties at design stage on the aspects of maintenance requirements.
The landscape design of roadside slopes should aim to reduce maintenance requirements
(e.g. clearance of overgrown vegetation) to the absolute minimum. It should take into account
the fact that space alongside a road is often limited and access to a roadside slope is often difficult.
Consideration should be given by the designer to the provision of a safe access for watering in the
early years of vegetation establishment and for inspecting the slope and landscape, and
maintaining vegetation in the long term. Account should be taken in the landscape design of
whether there is a suitable source of water nearby for initial watering purposes.
Where a vegetation cover is provided, careful management by the owner or his
maintenance agent in the early years of vegetation establishment will help to ensure that the
vegetation remains self-sustaining in the longer term. ong-term maintenance is fundamental
to the success of vegetative treatments. The use of fast growing non-native, pioneer tree
species to promote the establishment of other native plants, carries with it the need to remove
these plants entirely some 5 to 8 years to avoid them becoming dominant.
Where vegetation cover has to be cleared to facilitate the inspection of the slope,
provisions should be made for re-planting and regeneration of plant species. Other
maintenance operations that should be undertaken on a regular basis include repair of large
eroded vegetated areas on the slope and the general inspection of the health of plants. For
further guidance on the maintenance of landscape works, reference should be made to GEO
(1998a), GEO (2000), ighways Department (1996), SITEC (1991), rban Services
Department (1992), Works Branch (1993) and Works Branch (199.b).
When slopes with a chunam or sprayed concrete cover require maintenance works, the
opportunity should be taken to see if any part of the slope can be provided with a vegetation
cover instead (Works Bureau, 2000).