The federal government has been using its system of border checkpoints to greatly expand a database on travelers entering the country by collecting information on all U.S. citizens crossing by land, compiling data that will be stored for 15 years and may be used in criminal and intelligence investigations. The Border Crossing Information system, disclosed last month by the Department of Homeland Security in a Federal Register notice, ... reflects the growing number of government systems containing personal information on Americans that can be shared for a broad range of law enforcement and intelligence purposes, some of which are exempt from some Privacy Act protections. While international air passenger data has long been captured this way, Customs and Border Protection agents only this year began to log the arrivals of all U.S. citizens across land borders, through which about three-quarters of border entries occur. The volume of people entering the country by land prevented compiling such a database until recently. But the advent of machine-readable identification documents, which the government mandates eventually for everyone crossing the border, has made gathering the information more feasible. Critics say the moves exemplify efforts by the Bush administration in its final months to cement an unprecedented expansion of data gathering for national security and intelligence purposes. The data could be used beyond determining whether a person may enter the United States. For instance, information may be shared with foreign agencies when relevant to their hiring or contracting decisions.