Answers
The rapid urbanization in the world has increased the population in the cities. The better opportunities to earn money in the cities and preference by governments to invest in urban infrastructure as compared to rural infrastructure has attracted more people. However, modernization of such infrastructure in the urban has lagged the population growth rate and it also lacked planning.
The increasing population required higher share of available land for housing and that means lesser roads.
The clogging roads with increasing number of vehicles and population density resulted in frequent traffic jams and higher commuting time. That is nothing but waste of fuel and time.
This seems to be similar with the city A which has a higher commuting cost than city B. The city A might be having a steeper population density gradient.
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