Glossary of Key Terms

This glossary provides definitions for key terms used throughout the Biodiversity & Infrastructure Handbook, supporting consistent understanding across disciplines such as ecology, engineering, transport planning and policy.

Definitions are based on legal texts, reference documents and expert agreement, and cover essential concepts related to wildlife and traffic, habitat fragmentation, ecological connectivity, mitigation measures, monitoring, green infrastructure and nature-based solutions. The glossary helps practitioners interpret technical guidance and supports clear communication between stakeholders involved in infrastructure projects.

If you are new to transport ecology or working in a multi-disciplinary team, the glossary can serve as a quick reference before exploring detailed handbook chapters. Terms will continue to evolve as the handbook is updated through expert collaboration and user feedback.

Last update: October 2023 – How to cite

All | # A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
There are currently 23 names in this directory beginning with the letter C.
Canopy bridge 
See ‘Tree-top overpass’.
Carriageway
One of the two sides of a motorway or other large road, used by traffic moving in the same direction.
Catchment area 
Geographical area from which all precipitation flows to a single stream or set of streams (may also be termed as drainage basin, or watershed). In this handbook this may also refer to the area from which animals come to use a particular fauna passage.
Catenary
Overhead wires which support the contact wire on overhead line equipment in a railway.
Cattle grid
Ditch transversal to the road covered by metal bars which allows cars to pass over but prevent cattle and also some other species of wildlife to cross it. Usually installed when roads create openings in fences to avoid animal access into the fenced area.
Cattle passage
See ‘Drove road’.
Central reservation
See ‘Median’.
Clippings
Cuttings from herbaceous vegetation.
Cluster (roadkill cluster)
Road stretches with aggregations of animal vehicle collisions or road kills, stretches with a greater number of occurrences than would be expected by chance. Synonym: ‘Hotspot’. See also ‘Animal vehicle collisions’.
Community (biotic)
Assemblage of interacting species living in a given location at a given time.
Compensation
In terms of biodiversity, compensation involves measures to recompense, make good or pay damages for loss of biodiversity caused by a project. It differs from offsets in that compensation can involve reparation that falls short of achieving no net loss. See also 'Offsets' and 'Accompaniment measures'.
Compensatory measure
Measure or action taken to compensate for a residual adverse ecological effect which cannot be satisfactorily mitigated. See also 'Mitigation'.
Connectivity
See ‘Ecological connectivity’.
Conservation banking
A market where the credits from actions with beneficial biodiversity outcomes can be
Construction
Third phase of the infrastructure life cycle. It is when the infrastructure is physically built. The construction phase is the time when the effects of infrastructure development begin to show a real impact on nature. Strict adherence to all measures set to reduce environmental impacts is therefore a key consideration of this phase. See also 'Strategic Planning','Design','Operation and Maintenance', Decommissioning'.
Corridor
See ‘Ecological corridor’.
Crossing
Designated or recognised place for people or fauna to cross from one side of a linear infrastructure to the other. The crossing site could be provided by an structure (overpass or underpass) or take place directly over the carriageway or railway. See also 'Wildlife Crossing' 'Wildlife Passage'.
Crossroads
The intersection of two or more roads. Synonym: ‘Junction’.
Culvert
Buried pipe, box or channel structure, that allows a watercourse and/or a transport infrastructure drainage feature to pass under infrastructure.
Cumulative effects
The increasing impacts resulting from the combination of effects from several projects or activities over a period of time. Their assessment is called cumulative effect assessment (CEA).
Curb
See ‘Kerb’.
Currency
Unitary measures of biodiversity lost, gained or exchanged. This varies from very basic measures such as area, to sophisticated quantitative indices of multiple biodiversity components which may be variously weighted.
Cutting
V-shaped excavation of the land enabling transport infrastructure to be placed below the surrounding land surface.