Why traffic have been heavy in all the country

Because there are more and more people; they are richer and richer. They hope their life can be more and more convinient. So....

it is so commen in every counry I think,maybe because the number of people increases rapidly.there are more and more people in the earth and more and more cars in the streets.

Like what you said there are many manufacturers of different cars all over the world and they just don't stop manufacturing even they knew that it can cause traffic and of course competion from different companies of car. Each companies want to be the first to design and to show it from the public to buy. And the cause of it heavy traffic, in one family who buy a car but who has an old car but they did not disposed it or junk it. Like here in the Philippines even the oldest car are in the street even it is not good enough to use as long it's running they used it. They keep buying and buying new cars but they did not junk the old one.

Well so simple...yeah because of so many vehicles. Maybe your government shall try color coding juts like what the goverment here in one of the key city to avoid a heavy traffic. :)

Cars everywhere will keep increasing as people's salaries improve, and people always crave for a better means of transport. Once someone drives, he is not likely to give up his car, so the number of cars can only go upwards with time. Governments can keep traffic jams at bay by increasing the number of kilometres of roads built in tandem with car population increase. But there is usually a limit on this, as governments will not want to spend too much public money for road and bridge building. So governments have to tackle traffic jams in various manners. Some countries only allow certain cars to go on the roads on certain days of the week, say even or odd days. Some countries don't allow certain types of vehicles to go on certain parts of the city, while some charge for the use of certain roads where they want less cars. In Singapore, the government has been quite successful in controlling car population. They limit the number of licences which will allow someone to buy a new car based on how many cars were taken off the roads in the corresponding period the previous year. So if the increaese in road network allows only an increase of 2% in car population for this year, they will just set how many licences they can release for bidding by people who wish to buy new cars. Another measure used is to charge for going into the central business district and certain expressways, and this charge can be increased or decreased depending on the how heavily congested these roads are. The goal is to keep key major roads clearer of traffic.