Professor Ralston has wide experience in Scottish archaeology, and has been actively involved in the development of archaeological studies for environmental statements. He directed the archaeological studies for Shell Chemicals UK Ltd North West Ethylene Pipeline Project, the first major Environmental Assessment project conducted in Scotland in which archaeological considerations were prominent.

He established the Centre for Field Archaeology within the University of Edinburgh to conduct applied archaeological research on behalf of private sector developers and government agencies. He has advised council and local authority personnel in relation to archaeological matters preparatory to Public Inquiries.

Professor Ralston is a former Chairman of the Institute of Field Archaeologists. In this role, he commented on earlier drafts of the Scottish Office's NPPG 5 and PAN 42 documents and proposed modifications to the 1979 Ancient Monuments and Archaeological Areas Act, as well as a number of English Heritage proposals on archaeological practice. He is a former Councillor of the National Trust for Scotland and was active in establishing field archaeology as a concern of that body. He is a former member of the Scottish Environmental Standards Group.

He co-edited the new text, Archaeological Resource Management in the UK and the Institute of Field Archaeologists' Occasional Paper on Environmental Assessment and Archaeology. He is the author or co-author of over 115 papers and reports.