Last week we discussed level 1 and 2 autonomy and this week we will move on to L3-L5 which is considered to be “true” autonomous driving.
With L3 in certain situations (e.g., highway driving) the car can fully take over all driving tasks including lane changing, but the driver must be constantly paying attention and has to keep his/her hands near the steering wheel at all times and must be paying attention and not distracted by some other tasks such as watching tv, staring at a phone or sleeping. The reason the driver must always pay attention is that if the autonomous system finds itself in a situation it cannot handle (e.g., an unexpected detour or highway construction) it will provide a warning (e.g., seat vibrates or an alarm sounds) and then hand control back to the driver.
L4 is a fully autonomous car that can perform all driving functions without fail and doesn’t ever require intervention from the driver, though the driver has the option to take over at any time. The caveat however is that the autonomous function can ONLY be used in certain prescribed situations (e.g., proper weather conditions with certain visibility) or locations (e.g., in a well-mapped city or vicinity). Limiting autonomy to certain locations is called “geo fencing”.
L5 is the holy grail and doesn’t even require that a steering wheel or driver be present, though you could have either. At this stage, the autonomous function is presumed to be as good or better than any human driver and is capable of navigating any legal road in the country.