A8.7 - Visual impacts

Visual impacts

Landscape values are very subjective and the appearance of man-made structures in a natural setting may be pleasing to some and displeasing to others.

Roads that conform to the contours of the land are generally less intrusive than those through cuttings or on embankments.

In the urban landscape, the roadway is more than just a route for road vehicles; it is a public area for pedestrian movement and social intercourse, it allows light and air between buildings, and permits a view of the surroundings. Landscape elements such as proportion, exposure and enclosure, contrasts, long and short views, colour and lighting, hardness and softness of line, and architectural style all mix together to create the overall visual impact.

The negative visual amenity from living close to a traffic stream includes loss of privacy, night time glare from streetlights and passing vehicle headlights.

Visual impacts of roads

Visual impacts may be conceptually divided into:

• visual obstruction
• visual intrusion
• view from the road.

The visual impacts of roads and structures can be described as obstructive, in so far as they block the view, or intrusive when their appearance jars with the surroundings. Obstruction is more likely to be encountered in an urban setting.

In some cases a route may pass through an intrinsically attractive area and here the view from the road would be a consideration. The aesthetic appearance of urban and rural roads to road users should also be considered.

Mitigation of unattractive visual impacts

For projects which will significantly change the landscape, any aesthetic treatments based on impact assessments should be incorporated within the planning and design stages. Direct input of community values should be sought, given that visual impacts have a significant cultural component.

Visual impacts shall be assessed as follows:

(a) Visual obstruction

The magnitude of the visual impact caused by an obstruction depends on:

• size of the obstruction in relation to the viewing point
• quality of the view being obstructed
• visual quality of the obstruction
• numbers of people or properties affected by the obstruction.

The size of an obstruction can be dealt with by physical measurement. This requires the identification of viewpoints and a measure of the degree of obstruction received.

(b) Visual intrusion

This relates to the appearance of the landscape and is a broader concept than visual obstruction. Numerical predictive methods of measuring visual intrusion have so far not achieved general acceptance. Therefore, the appraisal of visual intrusion shall be based on subjective assessments of the appearance of the different options.

The existing scene can be observed but the proposed scene can only be imagined or represented either as artist's impressions, photomontage or physical modelling. Photomontage can now be generated quite realistically by computer image processing.

Perceived loss of amenity by persons located close to a road and its traffic, and loss of privacy, night-time glare from streetlights and vehicle headlights also constitute visual intrusion.

(c) View from the road

The types of scenery and the extent to which travellers are able to view the scenery need to be considered. Many New Zealand roads pass through scenic areas but, having numerous sharp curves, create a conflict for the driver between viewing the landscape and concentrating on safe driving. Changes resulting from the project can be presented either as artist's impressions or photomontage.

Reporting of visual impact

The visual obstruction and intrusion of projects shall be reported including, where appropriate, artist's impressions of the project and the numbers of people affected. The view from the road shall be reported in terms of the quality of scenery visible from the road and the types of people expected to benefit. Where artist's impressions or photomontage are used to assist description, care shall be exercised to give a realistic impression of the project.

Where projects have been modified to protect or enhance their visual impact, the incremental costs and benefits of these measures shall be reported.