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What are the autonomous car levels? Levels 1 to 5 of driverless vehicle tech explained

Published: 05 January 2018

► 5 levels in total
► Level 2 is currently becoming mainstream
► Audi A8 is Level 3 capable

If you’re interested in the future of transport, you’ll probably have heard of the autonomous vehicle levels. Simply put, they’re a set of guidelines determined by the Society of Automotive Engineers (SAE) to describe the differing levels of autonomy in driverless cars. There are currently with 5 levels in total, with one being the most basic and five being the most advanced.

What are the different levels of autonomy?

For last few years, car brands have begun to pick up and use the autonomous level terminology – the latest Audi A8’s Level 3 autonomous was heavily used during its promotion – but what the levels are, or what they actually mean isn't widely publisiced. To make things easier, we’ve explained every level of driverless tech, as well as who's in control, what features they include, and when they'll be on our roads.

Level 1: a single aspect is automated

The SAE, the Society of Automotive Engineers, has created a lexicon of autonomy. Level 1, the most basic type, is where one element of the driving process is taken over in isolation, using data from sensors and cameras, but the driver is very much still in charge. This started in the late 1990s at Mercedes, with its pioneering radar-managed cruise control, while Honda introduced lane-keep assist on the 2008 Legend. These were the first steps towards removing the driver’s duties behind the wheel.

  • When? The first steps in 1990s/00s
  • Includes: lane-keep assist, auto cruise control
  • Who’s driving? Driver IS in control

Level 2: chips control two or more elements

Level 2 autonomy is where we’re at today: computers take over multiple functions from the driver – and are intelligent enough to weave speed and steering systems together using multiple data sources. Mercedes says it’s been doing this for four years. This autumn’s updated Mercedes S-Class is Level 2-point-something. It takes over directional, throttle and brake functions for one of the most advanced cruise control systems yet seen – using detailed sat-nav data to brake automatically for corners ahead, keeping a set distance from the car in front and setting off again when jams clear, with the driver idle.

  • When? Current state of the art
  • Includes: lane-Change mode, self-parking
  • Who’s driving? Human hands-on at all times

Level 3: the car can boss safety-critical functions

Highly automated vehicles are not far off. The SAE calls Level 3 ‘conditional automation’ – a specific – mode which lets all aspects of driving be done for you, but crucially the driver must be on hand  to respond to a request to intervene. Audi calls its new A8, due this autumn, a Level 3 autonomous car – meaning the car has the potential to drive itself in certain circumstances, where it will assume control of all safety-critical functions. How? By refining maps, radar and sensors and fusing this environmental data with ever-wiser and faster processors and logic. Today’s assumption of a two-second comms lag will soon look very slow.

  • When? The next big thing: 2019-2020
  • Includes: next-gen sensors, algorithms, laws
  • Who’s driving? driver still on standby, but can be hands-off

Level 4: fully autonomous in controlled areas

Early next decade cars will fully drive themselves in geofenced metropolitan areas, as HD mapping, more timely data, car-to-car comms and off-site call centres (to deal with unusual hazards) improve accuracy. ‘You won’t really need the driver in Level 4,’ says Merc’s autonomous guru Christoph von Hugo. ‘The likelihood is you will just be renting the car, rather than owning it. You won’t take this car on vacation to Florida but you’ll take it on an urban journey around New York, say. It is easier to have ultra-detailed mapping for carefully defined areas.’ Twenty car makers say they’ll sell autonomous cars in the US by 2022.

  • When? Due early to middle of next decade
  • Includes: driverless cars, shared pods
  • Who’s driving? Genuine hands-off driving

Level 5: fully autonomous, anywhere. Driver optional

The difference between Level 4 and 5 is simple: the last step towards full automation doesn’t require the car to be in the so-called ‘operational design domain’. Rather than working in a carefully managed (usually urban) environment with lots of dedicated lane markings or infrastructure, it’ll be able to self-drive anywhere. How? Because the frequency and volume of data, and the sophistication of the computers crunching it, will mean the cars are sentient. It’s a brave new world – and one that Google’s Waymo car is gunning for, leapfrogging traditional manufacturers’ efforts. The disruption will be huge: analysts HIS forecast 21 million autonomous vehicles globally by 2035.

  • When? Not long after Level 4, mid next decade
  • Includes: Far-roaming robo taxis
  • Who’s driving? Steering wheel optional

By Tim Pollard

Editorial director of CAR's digital publishing arm. Motoring news magnet