Asked what they envision when prompted with the idea of 'Kathmandu', the Valley's leading urban planners and scholars respond in a variety of ways. Despite the differences in their conceptions of the Kathmandu Valley and the five municipalities that comprise it, none refer to a great deal of open or public space. And yet, it is just such spaces that help describe Kathmandu's past, while providing insight into its present and indicating future trends.
Three of the Valley's most famous open urban spaces surround the respective palaces of the Malla dynasty, which ruled between the 12th and 18th centuries: the Durbar Squares of the Valley's three main municipalities – Kathmandu (Yen) proper, Lalitpur (Yala, Patan) and Bhaktapur (Khwopa, Bhatgaon). Each of these squares is a cluster of temples, a palace, courtyards and raised dabali platforms. At dusk, one is free to climb the stairs on one of the temples in Patan Durbar Square, to sit and look out at the full performance of life below. Young children run about, while their older counterparts play slightly more structured games of catch, tag and hide-and-seek. Around the square, sales of cloth, vegetables, paper, spices and medicine take place; we could well be in Malla times, or the Licchavi period prior to that, or the Shah/Rana period following. If one concentrates, perhaps the children playing below are those of the palace attendants; the woman calling out to another is a member of the royal family, beckoning a member of her entourage. Behind a latticework window high up on the Taleju temple, you can observe a light and some movement. The king is doing puja to his protector deity.
And then the spell breaks. The door to the durbar opens, the word museum on a bronze plaque flashes by, and suddenly one notices the smell of exhaust. The sound of motorcycles and cars interrupts the brief voyage into the Valley's urban past. Indeed, the vehicles serve as a stark reminder of Kathmandu's evolution. According to the "Kathmandu Valley Plan for 2020", created by the Kathmandu Valley Development Committee, the number of registered motorcycles alone increased from some 24,200 in 1989 to more than 64,100 in 1995. By 2001, the Kathmandu Valley had 183,400 registered vehicles, at a growth of 21 percent per year. Growth of motorcycles continues at a rate of about 25 percent per year, while the numbers of buses and private cars plying the roads of the Valley had risen from 7069 buses and 18,000 cars in 1989 to 7557 buses and more than 28,900 cars in 1995. This data itself ends a dozen years ago, while in the intervening period the number of vehicles is said to have increased to well over 250,000.
The dramatic increase in the number of privately owned vehicles is a particular source of worry, both in light of the weakness of the Valley's road networks and the inevitable level of pollution. Kathmandu's bowl-shaped topography, coupled with its low winter wind speeds, makes the capital city acutely vulnerable to high rates of air pollution through the phenomenon known as 'temperature inversion'. Levels of so-called PM10 particles in Kathmandu's air – those that are able to lodge deep within the lungs, and are among the most harmful of air pollutants – are particularly high. According to studies done by the organisation Clean Energy Nepal, between 1993 and 1999 PM10 levels nearly doubled, to 225 micrograms per cubic metre, among the very highest in the world. And that rate does not look set to decrease anytime soon. According to 2002 estimates, PM10 concentrations in the Kathmandu Valley are to increase by some 82 percent between 1996 and 2011, with more than a third of this due to vehicle emissions. Meanwhile, the number of hospital patients with acute respiratory infections increases by around 23 percent every year. During the winter months, this illness is now the leading cause of death in the Valley.