SAN DIEGO (AP) — The busiest border crossing in the United States will close this weekend to the more than 40,000 cars that pass through it daily to Mexico. The closure between San Diego and Tijuana for work on a $741 million expansion project presents a monumental headache for border businesses, workers, tourists. The expansion is believed to be the largest renovation of a crossing along the nearly 2,000-mile-long U.S.-Mexico border.Read more on NewsOK.com