WASHINGTON—Tesla Inc defended the safety benefits of its advanced driver assistance system Autopilot and its Full Self-Driving (FSD) capability but acknowledged they require “constant monitoring and attention of the driver.” Democratic Senators Richard Blumenthal and Ed Markey wrote Tesla Chief Executive Elon Musk on Feb. 8 raising “significant concerns” about the electric-car maker’s Autopilot and FSD systems which have prompted scrutiny from safety regulators. In a previously unreported March 4 letter to the senators, Tesla’s senior director, public policy and business development Rohan Patel, said the features enhance the ability of its customers “to drive safer than the average driver in the U.S.” Patel noted that both systems “require the constant monitoring and attention of the driver.” Tesla vehicles are capable of performing “some but not all of the Dynamic Driving Tasks” that can be performed by human drivers, he added. Tesla says on its website that Autopilot enables vehicles …