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Historically, the appraisal of different transport modes in the UK has been undertaken on a separate and non-comparative basis. In recent years, Common Appraisal Framework (CAF) methodologies have been developed to assess various transportation measures against a series of objectives set for a clear definition of the problem to be addressed. These objectives comprise environmental, social equity and economic considerations beyond the confines of the traditional cost-benefit approach. CAF methodology is now evolving into a tool that facilitates not only the comparison of transportation measures on an equal basis across a wide range of topics, but also to assist in the formulation of transportation measures and the manner in which they are packaged into transportation strategies. The appraisals are consequently dealing with a variety of modes of transport and policy/fiscal measures. The UK approach to the environmental assessment of highways schemes is described in the Highways Agency Design Manual for Roads and Bridges (DMRB), Volume 11 (1993). This Manual specifies the approach to the assessment of highway alignment options (Stage 2 assessments) and the environmental design and assessment of the preferred scheme (Stage 3 assessments). The Manual does not, however address the potential environmental impacts associated with different means (different modes o