The growing need for underground transportation systems as an alternative to surface alignments, for space for trade, offices, social and recreational facilities and for service networks such as telephone cables, sewers, water, gas pipes, etc under existing surface structures, has increased the frequency of underground construction in highly urbanized areas.

As the construction costs of underground structures are generally higher than those of building on the surface, underground structures are in some ways " penalized " when compared to surface construction. However, when surface and underground projects are compared over the expected life of the projects, underground construction can prove more economic. Underground structures are generally energy conserving due to their removal from the effects of the changing surface climate. Similarly, by putting facilities underground, valuable surface land can be used for other purposes.

The decision-making process, when evaluating an underground project against a surface or aerial alternative, should not only refer to the construction cost, but should take into account the various advantages offered by the underground alternative, particularly those related to the effects on the environment.

For the above reasons it is particularly important that people involved in the design and development of underground space should work together and exchange their experiences as a means to promote the development and use of more underground facilities. In addition, technological development aimed at facilitating more risk-free underground construction must be pursued

The Congress will be a chance for International co-operation and exchange amongst the world’s community of planners, researchers, builders, investors, decision-makers and other parties involved in the development and use of urban underground space.