3. Notes on the analysis and evaluation of environmental impacts

Binding, universal guidelines for any complex analysis of the many and diverse aspects of the possible environmental impacts generated by the building of roads do not exist and given the many different sides there are to the problems it would be virtually impossible for them to be satisfactorily drafted.

Even the evaluation criteria developed for German conditions have so far proved impossible to define in quantifiable terms, except that is for the criteria for noise emission and the emission of harmful air pollutants (see the environmental brief Road Traffic). In view of the number of variables that there are, any ranking assigned to possible alternatives will continue to be largely subjective. The only answer to this problem is more thorough planning which brings out particular critical issues with greater clarity.

Preliminary regional planning and a detailed feasibility study including a comparative evaluation of all the adverse and beneficial impacts may therefore be a useful way of obtaining the information needed for assessing the widespread effects of a road-building programme.

An advance study of this kind will be made at an early stage and it is at this stage that a check should always be made to see whether the alignment corridors

- are suitable
- are suitable with the proviso that corrective measures still to be defined are carried out, or
- are not suitable.

For this purpose it will be necessary to draw up appropriate maps of protected areas, plans of the natural landscape, geological surveys, registers of land used for agriculture and forestry and maps of forests and woodlands, surveys of hydrological resources, and master building plans, to define the possible alignment corridors, and to evaluate alternative possibilities by a process of comparison.

The measures that will have to be taken to blend the road into nature and the landscape should be realistically shown and described in words in a special drawing (e.g. to a scale of 1 : 5000). After a comparative appraisal of the possible alternatives, all the details of these measures should be worked out and incorporated in the design drawings (e.g. on a scale from 1 : 2000 to 1: 500 with appropriate detail drawings).

Where it proves virtually impossible in the different planning phases for harmful factors to be quantified (and their impact to be rated or even costed) in relation to evaluation criteria and standards arrived at by analysis or ones for which standard procedures are defined, then qualitative approaches to evaluation may be successfully adopted.