Driverless cars: what they are, how they work and when they will arrive

Driverless cars are vehicles that can drive without a person controlling the steering wheel or the pedals, thanks to sensors, maps and artificial intelligence software that interprets the surroundings and makes decisions. Commercial robotaxi services already exist in some cities in the United States and China, but the cars sold in Spain offer at most advanced driver assistance, in which the driver remains responsible at all times. Fully autonomous driving, anywhere and in any situation, is not yet a reality.

Not so long ago it seemed like science fiction, and today it is one of the fields where carmakers and tech companies invest the most. In this guide we explain where things stand, how it works and what could change in passenger transport, including journeys to the airport.

To talk accurately about autonomous cars, people use the classification drawn up by SAE, the international association of automotive engineers, which distinguishes six levels. The key difference lies in who watches the road: up to level 2 it is always the driver; from level 3 onwards, under certain conditions, it is the system.

Most new cars with “autopilot” or “assisted driving” stay at level 2: they keep the car in its lane and at a set distance from the vehicle in front, but they require hands on the wheel and constant attention. The robotaxis that run with nobody at the wheel in some cities are level 4: they drive themselves, but only within the areas and conditions they have been prepared for.

A driverless car combines several technologies that complement one another, because none of them works well in every situation:

• Cameras that read signs, traffic lights and road markings and recognise pedestrians or cyclists.
• Radar, which measures distances and speeds even in rain or fog.
• Lidar, a laser sensor that builds a three-dimensional map of everything around the car.
• Ultrasonic sensors for manoeuvres at very close range.
• Satellite positioning and high-definition maps, which locate the vehicle precisely. If you are interested in how this part works, we explain it in the importance of GPS in driving.

All that information is processed by an on-board computer running artificial intelligence software trained on huge amounts of driving data. The system predicts what other road users will do and decides when to brake, turn or give way.

The most visible progress is in robotaxis: services where you order a car from an app and it arrives with nobody at the wheel. They operate commercially in some cities in the United States, with Waymo as the best-known example, and in several cities in China. Always within defined areas, mapped in detail and with remote supervision.

In Europe the roll-out is slower. Some carmakers offer level 3 systems on certain models and in very specific conditions, such as motorway traffic jams, and there are pilot projects for autonomous shuttles on sites and short routes.

In Spain, the DGT (the national traffic authority) has a procedure for authorising tests of automated vehicles on roads open to traffic, with specific safety and insurance requirements. Outside those tests, the systems on sale are driving aids and the driver is answerable for what the car does: they must stay alert, with their hands ready to act, and follow all traffic rules. The rules are evolving, so it is worth keeping an eye on the updates published by the DGT; we review some recent changes in what is new in traffic regulations.

Driverless cars raise fundamental questions for taxis: who helps with the suitcases, who deals with a last-minute change of terminal or who looks after an elderly person or a family with young children. A good taxi driver's knowledge of the city, which we talk about in the extraordinary brain of taxi drivers, is not easy to replace, and the human side of the service counts for a lot when it comes to making a flight on time.

The most likely scenario is a gradual transition in which driving aids make vehicles safer while the driver stays in charge. We look at how the service could evolve in the future of taxis in Madrid and what the vehicles might look like in the taxi of the future.

In the meantime, to get to Barajas you can count on professional taxi drivers licensed by Madrid City Council, 24 hours a day. From the centre, the fixed fare from inside the M-30 is €33, and from any other area you can book your airport taxi at a fixed price.