The self-driving car, whenever it arrives, is sure to be hailed as a breakthrough.

The truth is, autonomous cars have been arriving in bits and pieces for years. Bristling with sensors and microprocessors, cars — especially at the top end of the price spectrum — have long been lightening the driver’s workload and improving safety with features like parking assist, lane-departure warning, adaptive cruise control and various crash-avoidance technologies.

More bits of autonomous driving technology are arriving in the new model year.

“We’ve given the vehicles senses,” Ralf G. Herrtwich, director for driver assistance in the advanced engineering group of Daimler, the parent company of Mercedes-Benz, says in a video presentation for reporters. “They can see and do so much more.”

The car Dr. Herrtwich speaks about is the 2014 Mercedes S-Class, which arrived at United States dealerships this month. The car makes a significant step toward the ability to drive autonomously, using many types of sensors to gather data about driving conditions, including a stereo camera that lets it “see” by providing 3-D images, akin to human vision.

The new S-Class — an S550 and S63 AMG are first to arrive in the United States — offers a package of technologies, some of which are extra-cost options, that Mercedes calls Intelligent Drive. Among its many components are systems that can steer, brake, cover blind spots and watch for pedestrians and animals. One function monitors the road ahead to ensure that passengers are not jolted by potholes.