World wide, we see developing nations build new infrastructure as well as developed citeis rehabilitating and expanding their infrastructure to meet the demands of increased population, energy efficiency, and environmental awareness of the public. Working Group 20 of the International Tunnelling and Underground Space Association (ITA), focused on Urban Problems and Underground Solutions, has examined the current status of the use of underground space in the urban environment as it evolves with expanding cities and urban densification. This paper presents examples of the uses of underground space in cities, trends in Metro and radway planning, and gives and overview of aspects to be considered during the dicesion making process, in order to optimally include underground solutions.

Use ot eh underground is not restricted to mega projects. This paper presents innovative uses of space for storage, local transport, water conveyance and treatment, and commercial space. Underground solutions to urban problems were in the recent past only considerd if all other (above ground) solutions had been exhausted. If the underground opteions are considered at an earlier project stage, more optimal solutions will become possible. This overview of existing underground solutions for urban problems and the way they can help in the decision making process is intended to boost the consideration of the underground option for future projects.