If I have the power to change one thing in my hometown, I will choose to solve the problem of traffic jam. 
In previous times, my home town did not have so much cars. People lived in a quiet and pretty city, although it is small. However, with the development of economy, more and more people began to buy cars. What is more, taking the cheap price of some cars into consideration, even young people who are just having jobs choose to buying cars. So sometimes, some families own 3 cars. 
The most serious thing which is resulted from the increase of cars is the traffic jam. The city is small, the old road is narrow but hard to broaden because it is impossible to tear down the whole old city. But hardly can people live away from the old city in which have supermarkets and many wonderful shopping-malls. Not like those big cities which are also have the problem of traffic jam, my hometown has no way to relieve this problem, because the town is near the city, and we do not have any subway, if people who live in the town go to work in the city, driving by themselves seems to be the best way. Of course, there is another option, that is, taking buses, but it is always time-consuming.
And with the situation becoming more and more harsh, the parking lots cannot meet people's needs, although many parking lots nowadays choose to be built undergrounds. For example, some friends with me went to have dinner in a restaurant which is located in the center of city, we had to park our cars outside the city and walked to the destination.
In general, traffic jam seems to be not only a serious problem of big cities, but also some small cities in China. Too much traffic always cause many adverse effects on people's lives, sometimes even emotions. So the thing i want to change most in my hometown is the traffic jam.