The most convenient transportation in my country

In my country, the most efficient transportation is the subway. It is convenient to take a subway from one place to another. Because of the high speed, it only takes us a few minutes  ' time ("time" is not necessary but not grammatically wrong either) to go somewhere by subway. With abundant subway lines, we can go to nearly every place by subway. Also, the train can contain lots of people and the price is not high. In a word, the subway is really a good transportation in my country.

Very good!

The most convenient transportation in my country

In my country, the most efficient city transportation is the subway. It is convenient to take a the subway from one place to another. Because of the its high speed, it only takes us a few minutes' time (unnecessary) to go someanywhere by subway. With abundant/plentiful subway lines, we can go to nearly every place by subway. Also, the train can contain carry/transport lots of people (too many too many! like sardines in a tin) and the price is not high. In a word, the subway is really a good form of city transportation in my country.