uthor, however, notes that security concerns may affect modal choice. Recent experience with terrorism targets and accidents suggests that travellers may in the future prefer the security of road transport relative to rail, in addition to the time and flexibility advantages. It is unclear whether (relative to air) there is a clear security/safety benefit for high-speed rail. Hence, additional security/safety costs are likely to be required to be built into rail systems to counteract these travellers' concerns. 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 Water facilities are also vulnerable to security threats. Certainly in North America the risk of malicious attack is becoming an increasingly important factor in infrastructure investment decision making. Attack could take the form of direct action to contaminate water supplies. But widespread disruption would likely be effected more easily via cyber attack, disrupting power, communication and control systems. The effects can be demonstrated by the power failure in the northeastern United States in August 2003, in which a number of wastewater treatment plants failed, leading to environmental pollution and households being advised to boil water (Ashley and Cashman). This illustrates the interdependencies across infrastructures and the need to take a holistic approach to security. Economic growth and structure In all four chapters, economic growth, notably growth in per capita income, is acknowledged as the major determinant of the growth in the demand for infrastructure. Indeed it is the only variable explicitly used in the projection exercise with the exception of the chapter on water, where an attempt is made to quantify the impact of four drivers of change (socioeconomic, technology, environment and political) on projected expenditures for water infrastructure as a percentage of GDP after 2015. Bohlin et al. note that i