According to Business Insider
Protesters and ordinary New Yorkers noticed an odd sight in Midtown this week as President Donald Trump’s Manhattan home of Trump Tower was surrounded by dump trucks filled with sand.
Some have complained about the inconvenience caused by the trucks taking up a lane on a busy street, but they serve a very practical role in protecting the president.
The massive trucks filled with sand provide a dense, protective barrier in the event of a bomb.
This is hardly the first time the trucks have come out for safety. On New Years Eve, the 20 ton trucks hauled another 15 tons of sand and lined the streets of Times Square where thousands would gather. During the November 8 election, both Trump Tower, and the Javits Center, where Hillary Clinton watched the election results, were lined with the heavy trucks.
The New York Times reported in 1983 that the Reagans ate their Thanksgiving dinner as dump trucks filled with sand surrounded the White House in response to an apparent bomb scare.
— AFP news agency (@AFP) August 15, 2017