Fig. 25 Night-time lights showing the urbanisation of Europe The zone of influence of city regions spreads beyond the city limits.Dublin city and
its surrounding counties have a population of over 1.18 million people with a commuter belt of almost 90 km radius from the CBD. Paris has a population of 10 million with a commuter belt averaging 45 kmradius fromthe CBD. When groups of cities grow into each other, huge urban areas known as
conurbations are formed. These regions are polycentric, containing several city areas that are of similar importance. Examples of conurbations include Manchester and Birmingham in the UK. The Randstadt in the Netherlands has a population of sixmillion peoplewhich ismade up of themerging of over six large towns and cities in a radius of 50 km. New York City is a metropolitan area which has a population of over 20 million people and covers a conurbation with a radius of 64 km. City regions are also spreading into the surrounding countryside. This urban
sprawl eats up valuable farm and recreational land and adds to commuter traffic problems. Controlling the future growth of city regions is important in every country.