The self-driving future is almost here -- if you've got one of Tesla's Model S cars. Tesla CEO Elon Musk just announced that it'll be bringing its new automatic steering mode, simply dubbed "autopilot," to the Model S lineup in three to four months via a software update. Musk says you'll basically be able to "go between San Francisco and Seattle without the driver doing anything." He's also careful to point out this isn't true self-driving, just very powerful automatic steering (it was announced alongside the dual-motor Model S in October). The downside? It's only available on highways, and it requires one of Tesla's $4,250 "optional tech" package. Musk notes that the company's current technology likely won't be safe in suburban neighborhoods, which often have random obstacles like kids playing in the street. Eventually, you'll be able to have your Model S park itself or drive up to you in a parking lot -- just don't expect to do that on public roads.