Comparing United States and European Cities
It is common knowledge that European cities are much smaller and denser than American cities. But, the question is, why is this so? There are many reasons for it that actually make a lot of sense. Perhaps the first and most important cause for urban density in Europe is the high price of gas. Some countries have gas that costs up to four times what is charged in the United States. This would greatly increase the cost of commuting in Eurpoean cities thus encouraging citizens to live closer to where they work. And since many people would not be able to afford the commute, the city becomes denser. Sales taxes on cars are much higher in European cities so they are not as affordable or available to the general public as they are in the United States.
Also, electricity costs are extremely high in Eurpean cities so many people need to make frequent trips to the grocery store because they have a small refrigerator if any. Being in downtown is thus more convenient for these trips that need to be made so often. In Europe, it can be more profitable to be a farmer because of the large agricultural subsidies that allow farmers to live on the urban fringes. In Europe, many more resources are put into mass transit instead of highways so many people take advantage of the various rail and bus systems and end up living in a more dense setting closer to where they need to travel on a daily basis.
Perhaps another reason for these high density cities is that they were developed long before the United States' cities. European cities have been around for centuries long before mass transit and automobiles were developed so their lifestyles have adapted to this. They have also had longer to establish themselves as a city and work out the problems that many US cities are facing today.