A biometric exit system will begin to be implemented at airports across the United States by 2018, Homeland Security Secretary Jeh Johnson said during a speech at the Woodrow Wilson Center in Washington, DC. “For years Congress and others have urged us to develop a system of biometric exit,” Johnson stated on Thursday. “I have directed CBP (Customs and Border Protection) to begin implementing the system, starting at airports, in 2018.”

A system of biometric exit involves taking the fingerprints or other biometric data of those who leave the country. According to Johnson, CBP has begun testing technologies that can be deployed nationwide. The system, which was originally slated for a 2016 rollout, will be paid for by $1 billion in fee increases over a period of ten years.

Earlier this month, House of Representatives Homeland Security Committee Chairman Mike McCaul said a biometric system is imperative to prevent visa abuse by terrorists.

The Department of Homeland Security reported to Congress in January that there are hundreds of thousands of individuals in the United States who entered the country legally, but overstayed their visa.