A、Cars, buses, and trucks. B、Highways built outside of the city. C、Traffic lights. D、Reducing the number of buses and cars. C

Cities try to improve their transportation in order for cars, buses and trucks to travel easily on them. Large highways run through cities, so people can travel from their home to their job quickly. Also, cities have installed traffic lights to control the vehicles on the highways. Two cities experimented with public buses to reduce the number of automobiles on that street. In Rome, passengers on city buses did not have to pay for a bus ticket. In Stockholm, people paid a low price for a one-year ticket to travel on any bus, trolley car or train in the city. Finally, to increase the safety of people who walk, many cities have closed some streets to vehicles.