People congregate in towns primarily for economic reasons. The growth of industrial and marketing communities begins as the result of natural advantages and concentration of transporta tion facilities. Most towns grow because of the means of liveli hood or the cultural opportunities that they provide. Certain great cities, like London and Paris, combine all features; others, like Washington, are mainly political and cultural centres. The immense urban aggregations which have grown up around the harbours and railroad terminals of New York and London are unique in history and the result of a new set of forces that are encouraging a high degree of concentration. In proportion as the inventiveness of man has led to the introduction of standardized methods of production, of improved methods of communication and building construction and of sanitary equipment adaptable for crowded populations, it has been possible to expand cities to great size and yet to retain a comparatively high degree of effi ciency and wholesomeness. In general, however, modern cities, whatever their size, suffer from lack of intelligent planning and well-balanced distribution of buildings and open spaces.
In all civilized countries urban populations have increased rapidly during the past ioo years. In newer countries like the United States the urban growth has shown no signs of slackening during the present century. There are three outstand ing factors in this growth, apart from its extent, which are having a great influence on the form that it is taking. The first is the coming of motor vehicles and the consequent increase in the use of highways. Urban growth in the 19th century was dominated by the railroad which helped to promote concentration. In the loth century the railroad continued to expand slowly, while the use of the automobile as a supplementary means of transporta tion has grown enormously, particularly in the United States. In the United States alone, between 1905 and 1925, the number of passenger cars registered increased from 77,400 to 17,512,638, and the number of commercial trucks from 600 to 2,441,709. In America and Great Britain and on the Continent, great arterial highways and fast speedways, radiating from the surrounding cities, are being constructed to provide means of circulation for this means of transport.
second influence operating in recent decades has consisted of the great expansion of rapid transit facilities. City workers have thereby been enabled to live at a distance from their places of occupation, and the result has been that the most rapid urban expansion has been taking place in the environs of cities. New
York and London have been growing rapidly in their outskirts and actually diminishing in population in their central areas.
Powerful effects on urban concentration has been caused on the Western Hemisphere by the erection of buildings of much greater heights than has been possible in the past. The results of improved transit facilities, combined with the inventions of the steel frame method of building construction and the elevator, have produced the sky-scraper with possibilities of building con centration that have only been partially realized. (See ARCHI TECTURE.) The greatest problem of a modern city is to retain the advantages of reasonable and proper concentration in face of the tendencies for over-concentration or congestion. This con gestion is due not to lack but to wrong distribution of space. The original cause of the defects in city growth is in the lack of true purpose with which the land is laid out when urban growth first takes place.
The uncertainties caused by the arrival of railroad transportation and the diversion of energy from art to mechan ical engineering that accompanied the growth of manufacture pre vented much general progress being made in the development of civic art in Europe during the greater part of the 19th century. Sanitation and health conditions were likewise neglected. To im prove these conditions public health and town extension acts embodying some planning regulations were passed in Italy, Swe den and Germany between 1864 and 1875. Under Napoleon III. of France, Haussman directed the replanning of Paris by Des champs in 1853 and brought near to completion the remodelling of that city. The streets, places and gardens of Paris are splen didly proportioned in relation to its building heights and masses. The remodelling of central Vienna was carried out towards the end of the 19th century. At this time, Germany and Sweden were the most active countries in Europe in the development of town extension and the architectural planning of cities. Before the World War extensive town planning was done in Nuremberg, Dusseldorf, Cologne, Frankfort and Hamburg. Every great Prussian and Swedish city has its town planning department, and at the present time the degree of control of new building develop ment is probably greater in these countries than elsewhere Im mediately after the World War there was much activity in town planning in the devastated regions of France. A town planning act was passed in 1919. Other post-war work included plans for Salonika and the remodelling of Athens in Greece.