Test-riding the self-driving Porsche, a computer that carves curves

Porsche is currently the only company in North America to offer a rear-engine, rear wheel-drive car (let's debate the Smart Fortwo later). It is also the only sport/luxury manufacturer to offer a trio of plug-in hybrids in its current lineup — the Panamera, Cayenne, and 918. And it is (subjectively) the only brand to successfully deliver exquisite road feel with an electrically assisted system. So it should come as no surprise that the stalwarts from Stuttgart should scythe their own path toward an autonomous future.

In fact, the engineers working on this pre-production system, known internally as InnoDrive, insist that it isn’t self-driving at all, maintaining that an autonomous system must relieve the driver of making decisions in either the longitudinal or latitudinal dimension. Not to get all semantic, but here we quibble. Porsche’s system — which we experienced in a hacked first-generation Panamera Turbo — seemingly controls travel in forward motion, and quite effectively and efficiently we might add.

The system takes Porsche's adaptive cruise control — similar to others, which follow at or below a set speed, maintaining a safe distance based on the radar-measured velocity and behavior of the car being followed — and builds on it. It adds a wealth of satellite-derived geographic and road congestion information, as well as cues about posted speed limits and road condition garnered from its cameras, radar and a host of onboard sensors.

What this translates to is a car — a hypothetical, futuristic car — that can predict what is going to happen on the roadways and adjust throttle, brake, and transmission outputs to optimize performance and/or efficiency. So, if a sweeping right hand turn is coming up, followed by an uphill stretch, and capping off by a reduction in speed limit at the crest, the InnoDrive-equipped vehicle will use all of the known data to create a “prediction horizon” regarding optimal outcomes. This allows it to know at precisely what speed to take the corner, when to accelerate on the incline, and when to coast, brake, or drop down a gear and engine brake once at the top. In a pilot experiment, the result was a computer-driven Porsche that was 10% more efficient and 2% quicker than human drivers on the same route.