and be substitutive, as with the use of telework and teleshopping, although to date the overall impact appears to be relatively limited. The incidence on other infrastructures however may in fact be of a different nature, creating for example situations of close dependency which in times of technical breakdown, natural disaster or malicious attack may lead to cascading disruption of critical infrastructures. Finally, the complexity of dealing with several different infrastructures at once may be an important cost factor. Road construction works for example increasingly have to cross or handle other surface transport modes as well as pipelines for district heating, natural gas supplies, electricity cables and drainage systems. Indeed, the cost of managing such interaction with other types of infrastructure may well prove increasingly burdensome in the future, unless appropriate solutions can be found (e.g. the application of GIS technologies). INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISBN 92-64-02398-4 © OECD 2006 1. A CROSS-SECTORAL PERSPECTIVE ON THE DEVELOPMENT OF GLOBAL INFRASTRUCTURES TO 2030 In addition to the direct interdependencies described above, there are indirect interdependencies which result from the impact of infrastructure on patterns of human settlements. For instance, the automobile has historically favoured a more dispersed habitat, which has a bearing on the requirement for, say, water or electricity distribution. These indirect effects are particularly important for the longer-term perspective. Table 1.2 presents examples of such interdependencies and synergies among different infrastructures in a simple, illustrative matrix. 5. Cross-cutting issues and policy challenges The previous sections have considered the benefits that infrastructures can generate, explored how requirements for infrastructure services may evolve over the next thirty years or so, examined some of the main factors and uncertainties that may affect these projections, and identified some of 