The Schengen Agreement is a 1985 treaty that was signed by France, West Germany, Luxembourg, Belgium and the Netherlands, in which the countries agreed to take steps to reduce the border controls in place among them. Before World War I, it was possible to travel throughout Europe without a passport; border controls requiring the issuance and checking of passports began during the war and remained in effect after it was over. The Schengen Agreement was directed at removing these World War I controls. In 1990, a companion treaty was signed and, collectively, they are known together as the Schengen Agreement. Ultimately, the goal of the agreement was, over time, to enable the free movement of people between those countries.
To reach the goal of free movement across borders, the first steps taken by the provisions of the 1985 Schengen Agreement were for the treaty signatories to adopt a standardized system of policies involving both asylum and visa requirements. Passport checks were abolished; instead of stopping and searching every vehicle, ones with a green visa symbol on the windshield could drive straight through. A contingent of guards, however, remained on the borders to visually check vehicles passing through. At the same time, a very large database, the Schengen Information System, was compiled so the countries could share information across borders about both the people and the goods that were transiting what has become known as the Schengen area. In 1990, an amended Schengen Agreement took these steps further by making provisions that would lead to completely eliminating border checks.
The Schengen area operates very similarly to a single state, as far as international travel is concerned. There are border controls for people traveling in and out of the area, but no internal border controls exist. From its beginning with five nations, this borderless zone has expanded to cover more than two dozen countries in Europe containing a total population of more than 400 million people.
It took about 10 years for all provisions of the Schengen Agreement to be implemented. In that time, border posts were closed and frequently removed. Participating countries are required to eliminate all obstacles to the free flow of traffic at internal borders. Travelers should note that all of the regular border controls, such as the requirements to show passports and visas, continue to exist in order to enter the Schengen area. After entering the area, though, the traveler will be able to move freely across the internal borders of the countries that participate in the Schengen Agreement.