Tall buildings evolved from the economic imperative of maximising the return on prime building land in the financial and business sectors of cities. In a few cases it is probably true that the economic case was compromised by the additional kudos perceived in building taller than ever before. The tallest buildings in the world are not necessarily the most efficient.

  However, the great majority of tall buildings are the end product of an economic cost benefit process designed to yield a satisfactory financial return to developers and investors. Their height is that which is most appropriate to assessed consumer demand, which is in turn dependent on many factors including the prevailing business climate and the ease of access to transport systems. The demand for tall buildings will continue to be driven by the economics of return on investment.

  Should there be a continuing demand to build high, Government has the ability to choose what additional, if any, constraints it wishes to apply through the planning process.

  In reaching a view on this, Government should consider the issues of societal well-being, environmental impact and sustainability. Tall buildings can inspire and delight. At their best they are exuberant expressions of a vibrant civilisation. They can be a wonderful part of our civic landscape. Conversely, if designed without imagination or attention to detail (in all its senses), some have been abject failures as spaces to live or work. The failures of the 1960's housing blocks were due to many reasons, but perhaps mainly the failure to understand the user's interaction with the building. There are fewer examples of unsuccessful high-rise office buildings.

  There are other factors which merit consideration. Tall buildings in financial and business centres help preserve green spaces elsewhere. Tall buildings also allow public transport systems and public utility systems to be more focussed and efficient. High-rise Manhattan is more efficient, and arguably more sustainable, than the urban sprawl of Los Angeles.

  An alternative to tall buildings in city centres is promoted by some to be the idealistic concept of living and working in close proximity in relatively small suburban communities. Enforcing this would achieve certain aims of reducing the need to travel, but at the cost of compromising one of our basic freedoms to seek career advancement by changing employer. Whilst we aspire to a society which allows freedom to choose where we live and where we work, enforced dispersal of jobs into the suburbs would most likely lead in the medium and long term, as people changed jobs but not their homes, to longer and more varied journeys between suburbs, without the benefit of efficient large volume public transport radial arteries.

A NOTE ON 11 SEPTEMBER AND THE EFFECT ON TALL BUILDINGS POLICY

  Since the economic climate reflects the level of confidence in developers, investors, insurers and prospective tenants, there is no denying that the events of 11 September in New York have shaken our confidence in tall buildings as safe places to live and work. There are those who link the vulnerability of terrorist attack to the incidence of tall buildings and are seeking to cite the appalling terrorist attack on the World Trade Center as a reason to change Government policy on Tall Building planning constraints. Government would be wrong to do so. The incident was a vicious and horrible attack designed to inflict maximum damage and loss of life. The target happened to be a tall building, due perhaps to its association with capitalism. One could conceive of equally horrific consequences if the target had been, say, a suspension bridge full of rush hour traffic, or a baseball or football stadium when full to capacity, or a national iconic building such as the Houses of Parliament or Buckingham Palace. The root of the attack was the deeply entrenched resentment and hatred, which breeds terrorism. Building smaller buildings is no answer to that. The terrorist target, or means of attack, would simply change. Terrorists always attack the soft underbelly of civilisation. Our built environment is designed for peacetime and, as a consequence, our infrastructure has a degree of vulnerability. We have long evolved from the city state and have chosen as a society not to live in fortress cities. There is no logical case for 11 September to change this. Indeed, to do so would be a victory for terror.

  Investigations into the collapse of WTC will provide new information for architects, planners and civil engineers and help them design future tall buildings with greater intrinsic robustness, greater intrinsic safety, and more effective and rapid means of escape. (Indeed, design principles and understanding had already evolved from the mid 1960's when the WTC towers were designed.) The Institution of Civil Engineers is participating in a Study Group on Safety in Tall Buildings, which includes professionals from all relevant disciplines. This group is liaising closely with the investigation team set up by the American Society of Civil Engineers. It is expected that the final output from this group will be guidance for improving the design, the layout and the engineering detail of tall buildings.

  Government may wish to take note in due course of the Study Group's recommendations, and this would be an appropriate and sufficient response to the events of 11 September.

SUMMARY

  Tall buildings, if designed and built intelligently, should play a significant role in an advanced and developing city. Their economic viability depends on the confidence of developers, of insurers and of tenants. This has recently been shaken by the events of 11 September and the market will be making its own adjustments in response. Architects and civil engineers are assisting in the rebuilding of confidence by applying lessons learned from the attack on the World Trade Center. Governments can assist by addressing and resolving the deep conflicts which nurture terrorism.

  If the demand for tall buildings continues, Government policy should consider the potential benefits or disbenefits to cities by assessing not just the economic impact, but also environmental and sustainability issues. In this respect there are important benefits associated with clustering tall buildings in financial and business centres. Public transport systems and public utility networks can be more focused and cost-effective. Urban sprawl is prevented. Green spaces elsewhere are preserved. At their best, tall buildings are also exuberant expressions of a vibrant civilisation.

  Tall buildings, if designed intelligently and built well, with intrinsic robustness, intrinsic safety and rapid means of escape, should continue to be important features in our city landscapes and planning policy should reflect this.