You are going to drive abroad. If you are over 18 and you are going to drive abroad, first of all, you should take care of your International Driver License Translation. It doesn’t take much time since the International Driver License Translation is a translation of a National Driving Permit and doesn't demand any written permit and road test. The International Driver License confirms your right to drive vehicles of a corresponding category, but you have to remember that the International Driver License Translation doesn’t substitute your National Driving Permit and can be used for driving only as a supplement to your valid National Driving Permit. All the time, carry both your International Driver License Translation and your National Driving Permit.

You are going to travel to foreign country. If you are going to travel through a foreign county, the best way to do that is a car journey since you are independent from excursion groups and can move freely. However, if you drive outside of your home land, you may need an International Translation of Driving Permit. This is an addition to your National Driving Permit that you should to have with you if you are driving a car abroad.
Even if you are going to travel by plane or by train, or by bus and aren’t going to drive abroad, you can’t guess all situations in advance. Probably you will want to visit a place in which the public transport doesn't go; or you will need to drive a drunken acquaintance or friend; or it will be necessary to deliver someone in a hospital and except you nobody can do that; or something else. There can be hundreds situations in which you will are compelled to drive.

You are going to go in a business-trip. It is very difficult to accomplish business without a car; especially, if you need to move a lot. If you are going to go in a business-trip, you should obtain your International Driver License Translation  before you leave your home country.

 About Unofficial International Drivers License - International Translation of the Original Driving Permit