Last week, two big milestones in autonomous driving slipped by almost unnoticed.

One had to do with a commercial by Mercedes-Benz for the new E-Class. The car lets you drive without holding the steering wheel or using the accelerator and brakes for short periods (but also at very high speeds). However, they decided to pull the ad to avoid any confusion with fully autonomous cars from Google and  other companies.

The other big news item had to do with a Tesla statement about the accident that killed a Model S owner in Florida. The company says the automatic brakes were to blame for the accident, not the somewhat poorly named AutoPilot mode that steers, brakes, and accelerates automatically. It's a war of semantics.

It might seem confusing to the uninitiated. I've driven most of the recent makes and models that have automated driving features and a few that are fully autonomous. I've  been a passenger in the Cruise Automation car and the Audi TTS that can drive unassisted on its own around a racing track.

Before you buy a car with autonomous tech, be sure you know exactly what you are purchasing and how the car drives in multiple situations. There are many levels, and many engineering phrases, and many technical terms, but these options turn into white noise for anyone who wants to buy a vehicle that benefits from robotic technology. You're concerned with safety and automation. The industry is concerned with terms or promotional activity. How do you know the difference?

Automated driving will come in many forms, but what it all comes down to is personal preference. Driving is a highly personal activity. When I'm testing a new car, I sit in the driveway for about ten minutes adjusting the radio, connecting my phone, tweaking the mirrors and learning some of the features. Automated driving is the same way.

Here's an example. I've tested the Chrysler 200 several times. It's not exactly an autonomous car, but it does have automated features in the premium version. The car has a mode where it can control the steering, brakes, and acceleration for you. However, it's meant to work with your hands firmly on the steering wheel at all times. If you drive without steering, the car will veer slightly from side to side. Even then, the automations are designed for safety and are more pronounced. If you veer too far to the side of the road, the car nudges you back with a quick pull on the steering wheel.

Compare that to the Tesla Model S. The engineers wanted to imitate a real driver and how humans actually drive. When you let the car drive itself, it moves gently in the lane but mostly stays in the center. While the Chrysler stays automated for maybe a half-mile, the Model S can drive that way for an entire commute. It's not fully autonomous by any means, but it uses more artificial intelligence (in a good way).

There are many cars on the road today that fall somewhere between this. The Volvo XC90, for example, can use a platoon mode in traffic jams. It imitates the driver in front of you, so if a shiny new Corvette moves slightly to the side of the lane, the XC90 will as well. It imitates speed and steering to make traffic jams more bearable.

The main difference here has to do with the programming, the sensitivity of the sensors (and the number of sensors) but even the taste of the engineer in how aggressively or how subtle the driving feels. This is also true of adaptive cruise control, which adjusts your speed for the car in front of you automatically. It works differently in a Ford than a Mercedes-Benz, an Audi, or an Acura. 

That's why, before you decide to purchase any car with automated controls, go for a long test drive. Let the salesperson know you need to take some time with the settings. Try driving in traffic if you can, go on a curvy country road, and drive in an urban setting. Ignore most of the technical terms. Get behind the wheel and find out whether the car matches your tastes. It's a crucial undertaking.