A8.8 - Community severance

Community severance

Community severance is the dislocation and alienation a community feels as a result of roads which sever communities or hinder access. It includes the effect of traffic on security and mobility of people, particularly pedestrians and cyclists and the consequential effects on their movement patterns and interaction.

Impacts of severance

The effects of severance are initially experienced as increased travel times, and difficulty and anxiety in crossing or travelling alongside the road. The results of severance in the longer term are diversion of movements to other, possibly longer routes, and to alternative and possibly less favoured destinations, and the suppression of trips altogether. The degree of effect varies with a person's age, being more severe for children and the elderly. Also the effects of severance can become worse over time as a result of traffic growth on a route.

Assessment of severance impacts

The effects that need to be identified are the suppression of trips, the choice of less favoured destinations, the general feeling of dissatisfaction as a result of severance including the effects on pedestrians and cyclists by proximity to traffic, and changes to neighbourhood and community structures. To quantify these effects requires information on existing patterns of land use and community structures and interactions, particularly in relation to community facilities such as school, neighbourhood shops, outdoor recreation areas, public transport stops and places of work. Some changes in severance effect can be evaluated in a similar way to road traffic by calculating changes in travel times for pedestrians and cyclists and applying the travel time values given in this manual.

For existing traffic routes, severance impacts can be considered on the basis of increased or reduced costs to existing pedestrians crossing the road. The analysis should take account of any additional distance required to walk to a controlled intersection, the time spent waiting to cross and the crossing time. The extreme case of severance is a motorway with fenced reserves, which poses considerable barriers to vehicular traffic as well as pedestrian and cycle traffic. The degree of severance experienced will depend on the number and location of vehicular and pedestrian crossing points.

Reporting of severance effects

Any areas affected by severance shall be identified, described and, if appropriate, mapped. The location of community facilities and the effects of the project on the accessibility of these facilities, particularly for pedestrians and cyclists shall be reported. Travel time changes for cyclists and pedestrians should be included with other road user costs in the economic evaluation.

Main crossing points shall be marked and the numbers of crossing movements indicated. In the case of projects, such as motorways, which create major barriers, their effects on overall community structures shall be reported. Where projects have incorporated features to reduce community severance, the incremental costs and benefits of these measures shall be reported. The benefits of reduced travel times, particularly for pedestrians and cyclists, and accident savings, shall be quantified to determine incremental BCRs of these factors.