Self-Driving Cars: Everything We Know About Autonomous Cars

Self-driving cars, a.k.a. "autonomous cars," have been a hot topic for years now. But what exactly is a self-driving car? It's a vehicle that can move, navigate and make intelligent decisions on its own. Today's more advanced autonomous cars process information gathered through a bevy of sensors as they communicate with other vehicles, surrounding infrastructure and even satellites. If that sounds complicated, it's because it is. But we're going to do our best in this article to demystify driverless cars.

Just like there are steps to a goal, there are levels of automation for self-driving cars. Precisely six levels have been defined by a global association of more than 128,000 engineers and technical experts known as SAE International. The scale starts with Level 0, where you do all the driving, and ramps up to full autonomy at Level 5, where the vehicle does all the driving. The animation above illustrates each of the SAE levels. In the following detailed rundown, we've added our own half-level in the middle to represent some of the self-driving car technologies that are currently out in the marketplace.

For specific definitions of key terms, check out our glossary at the end of the article.

LEVEL 0: MINIMAL ASSISTANCE

How much are you driving?

Practically all driving is your responsibility. You must steer, accelerate and brake like the olden days. There are a few instances where the vehicle will step in to help but only in emergencies.

How much is the vehicle driving?

There is no self-driving at this level. The vehicle is more like an attentive passenger, notifying you if other vehicles are nearby or if you're drifting outside of your lane. It may be able to brake if it senses an impending collision, but it really doesn't do any of the actual driving.

Examples of vehicle technologies at this stage:

• Automatic emergency braking
• Forward collision warning
• Lane departure warning
• Blind-spot warning
• Parking sensors

LEVEL 1: BASIC ASSISTANCE

How much are you driving?

At this early stage, you are still doing nearly all of the driving. You'll receive one form of active assistance along with emergency intervention, but you're still required to be aware and fully engaged at all times.

How much is the vehicle driving?

This is the start of self-driving car technology. The vehicle offers partial driving participation, but not much. This is the level where the vehicle's advanced driver assistance systems (ADAS) are able to control a single component of driving. In addition to providing the systems mentioned above, it also either steers or modulates speed, actively managing your position within the lane or your distance from the vehicle in front of you. But it won't steer and control speed together.

Examples of vehicle technologies at this stage (one or the other):

• Adaptive cruise control
• Lane keeping assistance

LEVEL 2: ADDITIONAL ASSISTANCE

How much are you driving?

You're still doing the vast majority of driving, but the vehicle can now do more than one thing for you simultaneously. You still must make decisions and take action when doing things like changing lanes, and you'll likely have to take control if there are any significant bends in the road. In most cases you'll need to have an active hand on the wheel to provide assurance to the system that you haven't crawled into the back seat to take a nap. Even still, a well-tuned Level 2 system can really help ease driving fatigue.

How much is the vehicle driving?

Self-driving car technology progresses here by having an additional component. The vehicle can now actively assist with steering and speed management, and most of the latest systems do this down to a complete stop. Some systems will also automatically begin accelerating again if there is a lead vehicle to follow. The vehicle also continues to be a good watchdog, alerting you of any dangers and providing nudges if it thinks you aren't paying enough attention.

Examples of vehicle technologies at this stage:

• Adaptive cruise control with lane keeping assistance

LEVEL 2.5: ADVANCED ASSISTANCE

How much are you driving?

This is a half-step between Levels 2 and 3 and isn't an officially defined level in the SAE standard. Much like Level 2, you're still doing most of the driving, but now you're able to take your hands off the wheel when conditions permit. This level gives you a taste of autonomous driving during those hands-free stretches, but the ADAS may require that your eyes be looking down the road and not at your smartphone (it knows, trust us).

How much is the vehicle driving?

This level is where self-driving car technology begins to rely on externally sourced data, such as GPS map data provided by the manufacturer. The ADAS is more sophisticated because it can combine map data with onboard cameras to recognize traffic signs and other environmental elements. It can adapt to speed-limit changes, anticipate curves by slowing in advance, and even perform some lane changes automatically within designated areas.

Examples of vehicle technologies at this stage:

• Tesla Full Self-Driving beta (formerly known as Tesla Autopilot and also known as Tesla FSD)
• Ford BlueCruise
• General Motors' Super Cruise/Ultra Cruise

How much are you driving?

You remain responsible for the majority of driving and decision-making, but on certain roads you have the option to go completely hands- and feet-free (while remaining in the driver's seat, of course). You must be ready to resume control once you're notified that the vehicle is about to relinquish control.

How much is the vehicle driving?

At this level, self-driving cars begin to advance toward true autonomy thanks to an automated driving system (ADS), which is more advanced than ADAS despite losing a letter. When conditions permit, the vehicle can steer, manage speed, make lane changes and pass slower cars, all without driver input. An ADS also employs artificial intelligence (AI) to enhance situational awareness.

Examples of vehicle technologies at this stage:

• Mercedes-Benz Drive Pilot

LEVEL 4: ADVANCED AUTOMATED DRIVING

How much are you driving?

This is the future people dream about. You can choose to be a passenger in your own car (though you'll still need to sit in the driver's seat), or maybe you just hailed a driverless taxi and you're nowhere near the controls. As long as the vehicle is operating in a defined area, it does all the driving. You can still take over if it's your own car, but why do that when you can kick back and relax? The vehicle assumes all driving responsibilities in these areas. However, if you travel outside of these areas, you will have to assume control and drive.

How much is the vehicle driving?

At Level 4, self-driving cars can operate independently most of the time. Indeed, the vehicle can drive itself all of the time as long as it's within the limits of a defined area. Combining artificial intelligence with sensors and cameras, the automated driving system is further upgraded with connections via broadband networks to nearby infrastructure, vehicles and even pedestrians. It sees and knows more than you do about the surrounding environment and can process that information faster than you could ever hope to.

Examples of vehicle technologies at this stage:

• There are a few metropolitan areas being used for testing by various companies. Waymo has a fully autonomous taxi service called Waymo One that operates in both the Phoenix and San Francisco areas. Waymo also operates various self-driving test vehicles for data collection purposes that range from a modified Prius to the Jaguar I-Pace EV. Uber has self-driving food and package delivery programs running in Houston along with three cities in California: Los Angeles, Santa Monica and Mountain View. Uber has also partnered with Motional to provide Hyundai Ioniq 5 robotaxis in Las Vegas.

LEVEL 5: FULL AUTOMATED DRIVING

How much are you driving?

You can now be a passenger all the time, on any road, in any conditions. In some instances you may have the option to resume control, but that assumes there are controls in the car to begin with.

How much is the vehicle driving?

This is the holy grail: Self-driving cars are fully functional and the vehicle’s automated driving system is in control all of the time, connected to the surrounding environment by way of broadband and live satellite data. It knows and sees virtually everything you do and a lot of things you don't. Resistance is futile.

Examples of vehicle technologies at this stage:

• None, as level 5 is purely theoretical at this point.

At the lower levels — anything below Level 3 — claims of self-driving or autonomous capability are misleading. Level 3 is where true autonomy begins, and anything below should be considered support. There's a long road ahead to full self-driving cars (Level 5), which we may not see before 2040 or even 2050. Much of that has to do with infrastructure deficiencies rather than the vehicles themselves. As we move closer to achieving Level 5, cars should continue to get safer as long as we understand their limitations. We're aiming to provide you with the most honest and current information about the state of automation and all the players involved.

Glossary of terms:

• Automatic emergency braking: a driver assistance feature that identifies when a possible collision is about to happen and responds by automatically activating the brakes.

• Forward collision warning: a driver assistance feature that detects vehicles, pedestrians and other objects in front of the vehicle and triggers an audio, visual or vibrating alert to warn of a potential collision.

• Lane departure warning: a driver assistance feature that detects if your vehicle is straying outside of your designated lane and triggers an audio, visual or vibrating alert.

• Blind-spot warning: a safety feature that detects potentially unseen vehicles in the adjacent lane (your blind spot) and triggers either an audio, visual or vibrating alert.

• Parking sensors: a driver assistance feature that monitors the perimeter of your vehicle and triggers an audio or visual alert to warn of a potential collision.

• Adaptive cruise control: a driver assistance and safety feature that can automatically maintain a safe distance from the vehicle traveling in front of you. In some instances, it can bring your vehicle to a complete stop.

• Lane keeping assistance: a driver assistance feature that constantly monitors your vehicle and intervenes to prevent it from straying outside of your lane.

• Tesla Full Self-Driving beta (formerly known as Tesla Autopilot): Also known as Tesla FSD, this system incorporates adaptive cruise control, lane keeping assistance and blind-spot warning along with data gathered by Tesla to enable semi-autonomous driving.

• Ford BlueCruise: a system developed by Ford that incorporates adaptive cruise control, lane keeping assistance and blind-spot warning and adds GPS map and surrounding environment data to enable semi-autonomous driving on certain highways.

• General Motors' Super Cruise/Ultra Cruise: a system developed by General Motors that incorporates adaptive cruise control, lane keeping assistance and blind-spot warning and adds GPS map and surrounding environment data to enable semi-autonomous driving on certain highways.