Well, now we know what Elon Musk's "D" is. After cryptically foreshadowing it on Twitter last week, Tesla has pulled the curtain of "the D and something else", revealing them to by a dual motor all-wheel drive option for the Model S and an "Autopilot" feature which allows semi-automous driving on the highway (I had guessed the AWD, and semi-expected the autopilot).
Let's start with the D first. Each Model S version, the 60, the 85, and the P85 (respectively the 60 kWh battery, the 85 kWh, and the Performance model), can now be purchased with the dual drive AWD option, which adds a "D" at the end of their badge model name (ie. 85D). Benefits are obvious: Better traction, especially on wet or icy roads, better handling, better performance, etc.
Here's someone's test ride in the P85D ("have you head against the seat so your head doesn't snap back"):
One of the less obvious benefits of putting two motors in an electric car is that, unlike in the gasoline world, going AWD actually increases the range of the vehicle. So total EPA rated range for the bigger battery Model S goes from 265 miles to 275 miles.
How is that possible? Partly is because Tesla has engineered new efficiencies into the updated drivetrain, but it's because having two motors gives you more flexibility to only use as much power as you really need and to re-capture more energy when using regenerative braking.
The second part of the announcement, and the more surprising thing, really, is that Tesla has "accelerated" its introduction of self-driving cars (which they call Autopilot, a term that people are more familiar with thanks to airplanes). In practice, what this means is that all Model S EVs produced in the past two weeks - and going forward, obviously - have the necessary hardware to support Autopilot.
This hardware includes a radar looking ahead, cameras, and a 360-degree ultrasonic sonar. These give the vehicle awareness of its surrounding as illustrated below. Autopilot will be updated over time with software updates, but as of today, it can read speed limit signs and keep the car at the speed limit on the highway. It can also automatically change lanes if the space in the next lane is free after the drive asks it to by activating the turn signal.
Over time, Autopilot should be able to self-park, do parallel parking, automatically park in your garage, etc. It's easy to imagine that over time it'll become more and more autonomous, though just the "assisted driving" features could help with safety (such as notifying you of lane departure and such).
Here's a video that shows Tesla's Autopilot feature in action at Tesla's event:
Here's USA Today with Elon Musk:
The AWD "D" variants for the 60D and 85D will carry a $4,000 price premium over the RWD version, and the top-of-the-line P85D will be $14,600 pricier than the already expensive P85.