A well-known challenge in planning is for the professionals involved to handle multiple sources ofknowledge and to influence decision-making as a result. This challenge is the main focus of this research and in order to explore it I have directed attention to the integration of knowledge pertaining to landscape in practices of transport planning. In particular, this re­search considers the professionals who contribute to such integration. The aim is to develop and refine our understanding of the challenges and opportunities professionals face when integrating knowledge oflandscape into the practices oftransport planning. A second aim is to contribute to an ongoing discussion within the field of planning theory that addresses the use ofknowledge and the logics underlying practices oftransport planning. At the centre of analysis are the professionals taking part in transport planning and their reflections on their own professional practice. Their perspectives are analysed in relation to the procedural and institutional aspects of their practice and in relation to previous research conceming professional knowledge, within the fields of planning, practice and organisations studies. Findings are presented in three separate studies that focus on different groups of planning professionals working in different parts of Swedish transport planning practice. Study I, investigates strategic planning performed at Regional Development Councils. Study Il sets eyes on the processes of förmal planning and design at the Swedish Transport Ad­ministration (STA) and Study III focuses on planning and design practices taking place at consultancy companies commissioned by the STA. Study IV differs from the other three, as it is primarily a theoretical discussion focusing on the knowledge oflandscapes. Study IV ad­dresses critical issues and challenges regarding the formation ofknowledge about landscapes in spatial planning contexts, based on published landscape research and planning theory.

This research provides situated accounts of professionals' reflections of their own roles, tasks, and practices. The main contribution lies in the details and nuances of their descrip­tions as these deepen our understanding of the complexity of landscape consideration and knowledge integration in transport planning. Participating professionals elucidate essential aspects of challenges in integrating knowledge of landscapes and additionally outline ways to make the interrelation of different types ofknowledge possible. Professionals' discussions provide insights into their perceived opportunities to influence planning decisions and ways they try to safeguard landscapes (rnitigate negative effects and create positive effects) in the layout and design of transport structures.