Glossary

Above Ordnance Datum (AOD)

The mean sea level at Newlyn (UK) used as a base measurement on Ordnance Survey Maps for contours.

Alluvial deposits

Loose clay, silt, sand, or gravel that has been deposited by running water, typically in a stream bed or on a floodplain. It is generally geologically young and not solidified into rock.

Assessment

An umbrella term for description, analysis and evaluation.

At-grade (junction)

A junction arrangement at which two or more roads meet at the same level.

Average Annual Daily Traffic (AADT)

The total annual volume of traffic on a road divided by 365 days to give average daily traffic volumes.

Baseline

The existing conditions which form the basis or start point of an environmental or traffic assessment.

Bedrock

Hard rock that lies beneath superficial deposits of soil and sediment.

Biodiversity

Biological diversity, or richness of living organisms present in representative communities and populations.

Broadleaf

Deciduous, broadleaved trees.

Carriageway

Part of the road constructed for use by vehicular traffic. Carriageway includes turning lanes, bus lanes, crawler lanes and acceleration/deceleration lanes.

Catchment

An area defined by watersheds (For example hill summits and ridge lines) contributing flow to a point on a drainage system.

Chainage

A distance measured in metres along the centreline of a carriageway or railway. Used as location references.

Conifer

Coniferous, evergreen trees.

Conservation Area

Area of special architectural or historic interest, the character or appearance of which it is desirable to preserve or enhance. Designated under section 61 Planning (Listed Buildings and Conservation Areas) (Scotland) Act 1997.

Core Path

Paths, waterways or any other means of crossing land to facilitate, promote and manage the exercise of access rights under the Land Reform (Scotland) Act 2003.

Culvert

A metal, wooden, plastic, or concrete conduit through which surface water can flow under or across roads.

Cut

The process of digging down and removing soil to create the road's intended level.

Differential Acceleration Lane (DAL)

A WS2+1 section of road on which the overtaking lane is provided for traffic accelerating away from a roundabout to cater for the differential acceleration between vehicles.

Departures from Standard

Where the design requirements outlined in the DMRB are not met, a Departure from Standard application must be submitted and accepted by the Overseeing Organisation to allow the sub-standard element to be included in the design.

Design Speed

The speed used to determine geometric features using design parameters set out in the DMRB.

Desirable Minimum

The minimum value associated with a geometric design feature, without relaxations or Departures from Standard.

Do-Minimum

Scenario assuming minimum interventions, which would likely need to take place in the absence of a proposed scheme. Provides the baseline for proposed scheme to be assessed against.

Effect

The result of change or changes on specific environmental resources or receptors.

Element

A component part of the landscape or environment (For Example roads, hedges, woodlands).

Embankment

A raised structure of earth or rock fill constructed above the natural ground level to elevate the roadway or track.

Environmental Appraisal Report (EAR)

An appraisal of key environmental constraints and potential environmental impacts associated with the proposed scheme.

Fill

Material deposited by man in ground depression or excavated area or to construct an embankment.

Flexible Pavement

Pavement constructed with a bituminous surface course, layers of quality aggregate and subgrade beneath which enables the pavement to deflect under load.

Floodplain

Land adjacent to watercourses, which are subject to regular flooding.

Fragmentation

Breaking up of an organism's habitat into smaller fragments that may vary in size.

Glacial Till

Part of glacial drift which was deposited directly by the glacier. It may vary from clays to mixtures of clay, sand, gravel and boulders.

Glaciofluvial

Pertaining to streams fed by melting glaciers, or to the deposits and landforms produced by such streams.

Grade Separated Junction

A junction arrangement that is separated by level from the through carriageway.

Ground Investigation

Exploratory investigation undertaken by drilling boreholes, excavating trial pits and various other techniques to determine the ground and groundwater conditions present, and the engineering properties of materials encountered.

Groundwater

Water that is present beneath Earth's surface in soil pore spaces and in the fractures of rock formations.

Habitat

Term most accurately meaning the place in which a species lives, but also used to describe plant communities or agglomerations of plant communities

Headroom

The height clearance from existing ground level to the underside of a bridge deck.

Heavy Goods Vehicle (HGV)

Vehicles with 3 axles (articulated) or 4 or more axles (rigid and articulated).

Hydrology

The scientific study of the movement, distribution, and quality of water.

Impact

Any changes attributable to the proposed scheme that have the potential to have environmental effects (the causes of the effects).

Impermeable

Material that does not allow fluids to pass through it.

Landform

Combination of slope and elevation producing the shape and form of the land surface.

Landscape

Human perception of the land, conditioned by knowledge and identity with a place.

Landslide

A general term which can be used to represent a number of different types of downslope movement of material (including Debris Flow), ranging in volume and speed of movement. The term may also be used to describe historical landscape features which indicate that movement has occurred at some time in the past. Depending on the size and nature of the landslide, and the erosion which has occurred since, the visibility of such features and the accuracy with which their age can be determined is highly variable.

Lay-by

A part of the road set aside for vehicles to draw out of the traffic lanes and wait for short periods.

Listed Building

Building included on the list of buildings of special architectural or historic interest and afforded statutory protection under the ‘Planning (Listed Buildings and Conservation Areas) (Scotland) Act 1997’ and other planning legislation. Classified categories A – C(s).

Local Road

An A, B or C classified road (non-Trunk Road) typically operated by a local authority or council.

Made Ground

Material deposited by man, not natural.

Mitigation

Term used to indicate avoidance, remediation or alleviation of adverse impacts.

Native

A species occurring naturally, in its normal geographic range.

Noise

Unwanted sound.

Parapet

A low protective wall along the edge of a bridge or other structure. Its primary functions are to provide safety by preventing people from falling. / A safety barrier installed on the edge of a bridge or retaining wall or similar structure where there is a vertical drop.

Peat / Peat Bog

A partially decomposed mass of semi-carbonised vegetation which has developed under waterlogged and anaerobic conditions, usually in bogs or swamps.

Plantation

An area in which trees have been intentionally planted.

Relaxations

A reduction of the design of a geometric design feature, below desirable minimum, where permitted in the DMRB.

Road Restraint System (RRS)

General name for vehicle restraint system or pedestrian restraint system used on the road.

Runoff

Water that flows over the ground surface to the drainage system. This occurs if the ground is impermeable or if permeable ground is saturated.

Scheduled Monument

A monument which has been scheduled by the Scottish Ministers as being of national importance under the terms of the ‘Ancient Monuments and Archaeological Areas Act 1979’.

Scottish Transport Appraisal Guidance

A guide for transport practitioners working on Scottish based transport projects, or any other interested party, with access to the latest information and guidance that they will need when developing and assessing transport schemes and strategies.

Severance

The separation of communities from facilities and services they use within their community. Alternatively, in relation to agricultural land, the division of plots of land into separate land parcels, potentially affecting access or creating areas that may be impractical for agricultural use.

Sites of Special Scientific Interest (SSSI)

Areas of national importance. The aim of the SSSI network is to maintain an adequate representation of all natural and semi-natural habitats and native species across Britain. The site network is protected under the provisions of Sections 28 and 19 of the Wildlife and Countryside Act 1981 as well as the Amendment Act 1985 and the Environmental Protection Act 1990.

STATS19

A collection of data for all road traffic accidents that resulted in a personal injury and were reported to the police within 30 days of the accident.

Statutory Bodies

Statutory Bodies are bodies that have been given statutory powers in relation to functions that are of a ‘public’ character.

Strategic Environmental Assessment (SEA)

The process by which information about the environmental effects of proposed plans, policies and programmes are evaluated.

Strategic Transport Projects Review 2 (STPR2)

STPR2 is a Scotland-wide review of the strategic transport network across all transport modes, including walking, wheeling, cycling, bus, rail and car, as well as reviewing wider island and rural connectivity.

Superficial Geology

The youngest, unlithified soils and sediments of the most recent period of geological time, the Quaternary, deposited during the last 2.6 million years and which overlie bedrock.

Surface Course

The top layer of pavement construction, typically flexible asphaltic material to provide durability, safety and resilience.

Sustainable Drainage Systems (SuDS)

A sequence of management practices and control structures designed to drain surface water in a more sustainable fashion than some conventional techniques.

Topography

The surface shapes and physical features on the ground and their arrangement.

Trunk Road

A major road, usually connecting large urban areas, ports, airports, and other strategic locations within a country. It's typically part of the national road network and is designed to carry high volumes of traffic over long distances.

Vehicle Activated Signs

Traffic signs that display a message or warning only when triggered by a specific characteristic of an approaching vehicle, such as its speed or type.

Viaduct

A long bridge-like structure, typically a series of arches, carrying a road or railway across a valley, river, or other obstacle. Viaducts are typically at a high elevation above the terrain being crossed.

Water Quality

The chemical and biological status of various parameters within the water column and their interactions, for example dissolved oxygen, indicator metals such as dissolved copper, or suspended solids (the movement of which is determined by hydrological process and forms geomorphological landforms).