Home > Associated groups > Strategic Environmental Assessment > Environmental Report > 5 Scope of Assessment
5.1 Introduction
The subjects addressedwithin the Environmental Report have been determined mainly through exploringthe environmental and transport related problems and opportunities that existwithin the WMMA. The scope of the SEA has been defined by a list of potentialeffects which are then represented by SEA objectives and indicators. This processhas also been aided by reference to research done by Somerset County Counciland TRL on significance criteria for LTP SEAs (TRL, 2004). Table5-1 shows the list of potential issues.
Table 5-1 The scope of the assessment
Comment on factors defining significance
The scope of the assessment will focus on…
Biodiversity
Effects range from loss of habitat, habitat fragmentation, direct mortality effects on species and changes in air quality that can affect ecological communities. The adoption of an ecosystem approach (which values all biodiversity not just the rarest and protected) means that potentially all areas have special characteristics. Rather than only assessing direct impacts on valued ecosystems a variety of issues is to be considered including potential habitat fragmentation, land take and habitat loss, hydrological changes and air quality and water quality.
- Actions that cause changes in habitat fragmentation or habitat loss.
- Actions that exacerbate loss or fragmentation of habitat affecting protected or priority species.
- Actions that affect areas where biodiversity is already exposed to significant threat.
- Actions that help to reach targets or compromise targets of BAPs.
- Actions that affect Natura 2000 sites, SSSIs or other designated sites.
Air Quality
Traffic produces 70% of carbon monoxide emissions, 48% of nitrogen oxide emissions and 22% of particulates. In general, air pollution affects people up to 200m away from the traffic source. However, pollutants like Ozone and PM10s are long distant pollutants. A traffic flow change of over 10% is considered to be potentially significant, although in AQMAs any change may be considered significant.
- The land use within 200m of a 10% traffic change focusing specifically on sensitive receptors such as houses, schools and hospitals.
- Changes in traffic affecting an Air Quality Management Area.
- Air pollution adjacent to species and habitats known to be susceptible to deterioration in air quality (any change in flows would be a concern).
Climatic Factors
Traffic contributes an increasing proportion of UK greenhouse gases.
- Changes in traffic flow or a change in the make-up of traffic that would cause increases in fuel use and CO2.
- Parts of the transport system prone to flooding and stability problems.
- Actions that substitute alternative fuels or energy sources for fossil fuels.
- Actions that will increase the use of alternative energy in the transport system.
Material Assets
The impacts may comprise the consumption of aggregates, the sterilisation of resources or the loss or relocation of other assets such as development sites or other urban infrastructure.
- Actions that change the use of recycled materials in road construction and maintenance.
- Actions that cause changes in the demand for aggregate.
Soil
The use and construction of transport infrastructure impact upon on soil composition and quality through loss, compaction and pollution. All infrastructure development will have impacts on soil. Increases in traffic and changes to the de-icing regime, for example, can have impacts upon soil. However, guidance on SEA and biodiversity (Countryside Council for Wales et al, 2004) recognises that transport will have relatively minor impacts on soil composition compared to other forms of development.
- Changes in existing soil erosion problems including effects of road maintenance
Water resources
Pollution of watercourses can occur from highway run-off and pesticides from verge maintenance as well as accidental spillage. In terms of magnitude, moderate impacts occur on roads with 15000 to 30000 vehicles per day. Below 15000 vehicles per day minor impacts still occur (Design Manual for Roads and Bridges, volume 11). The construction of transport infrastructure can also alter local hydrology.
- Changes in traffic flows or new infrastructure that could cause a change in water quality especially affecting good quality watercourses or those known to be of a high biodiversity value.
- Infrastructure that could cause a change in the flood risk.
- Watercourses of ecological importance affected by run-off from new or existing roads.
Human Health – Noise
Traffic is a significant factor in ambient noise. The effects reduce with distance with the opportunities for compensation under regulations being limited to 300m of the road. The size of the effect varies with the percentage of HGVs and traffic speed as well as the road surface condition. Government guidance suggests that changes in traffic flows of 20-25% are required to bring about a perceived change in noise.
- Sensitive receptors within 200m of a noise change focusing schools and hospitals.
- Areas which are likely to experience a 25% increase or 20% decrease in traffic flow.
- Areas where changes in speed are expected or areas will be resurfaced with a different material or managed differently (installation of speed cushions etc).
- Areas where the noise profile is likely to change in nature because of a change in HGVs or timing of traffic.
Human Health/Population – Safety, crime and health
Impacts on health are likely to vary with the levels of traffic. Congestion can also affect the emergency services. Maintenance of footpaths is also important for pedestrian accidents, particularly the elderly.
- Actions that cause changes in the risk of accidents on existing infrastructure.
- Actions that introduce increased / decreased opportunities for physical exercise.
- Actions that introduce increased / decreased security on the transport network specifically related to car crime.
Cultural heritage
Traffic and highway infrastructure can have varied effects on roadside historic buildings, monuments, Conservation Areas and historic landscapes. New infrastructure schemes and changes in traffic flows on existing roads may have a permanent effect on cultural heritage…
- A change in traffic flows or the nature of traffic through areas of historic / cultural value.
- Changes to infrastructure that affect historic landscapes, sites and monuments valued for their cultural heritage.
Landscape
Traffic and highway infrastructure can have an impact on landscape and tranquillity in the countryside. Increased traffic can have various effects in terms of direct effects such as visibility and also a contribution to more complex changes in countryside character including sense of place.
- Changes in traffic flows in areas that are valued for their landscape character.
- Introduction of new infrastructure to existing highways such as highways signing, lighting and highway furniture such as noise barriers.
- Introduction of traffic to previously tranquil areas.
Townscape
Traffic can affect the quality of urban centres and the townscape within them. It can impact upon the form of a town, its important views and panoramas. New infrastructure and traffic management can have a long term effect on the quality and feel of settlements. Townscape is also about form and function.
- Changes in traffic flows or the nature of traffic (an increase in HGVs for example) that could alter the character of the area or benefit townscape.
- Introduction of new infrastructure to existing highways such as highways signing, lighting and highway furniture such as noise barriers.
- Enhancement schemes that reflect the character of the townscape.
Population – Community severance
Both new roads and traffic changes on existing roads may change severance which can have greater effects on the least mobile and younger members of society. Railway lines and canals can also cause severance which in many ways is more serious because of the lack of crossings usually provided for these types of infrastructure. Research in the USA has shown that lightly trafficked streets (under 2,000 AADT) present few problems to residents in enjoying their living space and making contact across the road; medium trafficked roads (6,000 to 16,000 AADT) no longer affords the street to be a positive community space, although traffic is neutral and not intrusive in homes; and heavy trafficked roads (over 16,000 AADT) incurs no contact across it, and traffic is seriously intrusive.
- Increased or decreased traffic or a change in the nature of traffic (more HGVs for example) in residential areas and town / village centres.
- A reduction in the level of severance (i.e. crossing facilities, flexible and mobile services etc.)
Population – Accessibility
The LTP is an influencing factor on the provision of public and community transport but decisions by private operators are the most important influence on accessibility. Access to services and public transport is likely to be more demanding for those without access to a car.
- Changed provision in public and community transport that makes key services (schools and learning, open space and recreation, jobs, leisure facilities, areas of cultural heritage and health facilities) more / less accessible.
- Changed provision in public and community transport that is likely to affect a certain group of people or community. For example, increased provision of low entry buses to help the elderly and disabled.