The engineers who created the plan - Mendoza, González Echarte, and Otamendi - then began the process of raising 8 million pesetas to begin the first phase of the project, the construction of Line 1 from Sol to Cuatro Caminos.

[13][14][15][16] At the time of inauguration, the metro had just one line, which ran for 3.48 kilometres (2.16 mi) between Puerta del Sol and Cuatro Caminos, with eight stops.

[13] The king, the royal family, and others took part in the first official metro ride which went from Cuatro Caminos to Ríos Rosas and took 40 seconds.

[17] The Company then began to gather materials necessary to expand the Line 1 from Sol with the new stations Progreso, Antón Martín and finally Atocha.

In the 1960s, a suburban railway was constructed between Plaza de España and Carabanchel, linked to lines 2 (at Noviciado station with a long transfer) and 3.

[21] In the early 1970s, the network was greatly expanded to cope with the influx of population and urban sprawl from Madrid's economic boom.

After all those projects, 100 km (62 mi) of rail track was completed by 1983[22] and the suburban railway had also disappeared since it had been extended to Alonso Martínez and subsequently converted to the new Line 10.

Work on a major expansion of the metro began in 1995, with 172 km (107 mi) of new line and 132 new stations opened by 2011, built in 4 phases.

As the metro line is part of a project to develop the area, some stations lay in sparsely populated places or were even surrounded by fields at the time of opening.

For the first time in Madrid, three interurban light rails (Metro Ligero or ML) lines were built to the western outskirts (Pozuelo de Alarcón, Boadilla del Monte) – mL2 and mL3 – and to the new northern districts of Sanchinarro and Las Tablas – mL1.

The Great Recession and subsequent European debt crisis, which affected Spain particularly hard, brought metro expansion to a halt as austerity measures all but dried up available funding.

In recent years, most of these stations have been refurbished with single-coloured plates matching those in the newest ones, alongside other improvements such as modernized signalling technology and elevators.

Similar installations exist in some mainline rail tunnels where space is limited, e.g. Leipzig City Tunnel or the lower level of Berlin Hauptbahnhof, The Metro conventional network has 242 stations on 12 lines plus one branch line, totalling 294 kilometres (183 mi),[25] of which approximately 96% of stations are underground.[n.

Most of the ML track length is on surface, usually running on platforms separated from normal road traffic.

Notes: Traditionally, the trains operating in the Madrid Metro have been built and supplied by the Spanish company Construcciones y Auxiliar de Ferrocarriles (CAF).

In contrast, the B sub-series train sets can be told apart by its sleeker, rounder forms, which has granted them the nickname of "bubble" (burbuja) for their round driver cabin window.

Series 2000B were delivered in lesser numbers (about 126 cars) between 1997 and 1998,[28] with the inclusion of air conditioning and station announcements through pre-recorded voice messages and LED displays.

The final subseries, 5500, has a distinct, darker color scheme and returns to the usual on-demand opening of train gates with a button on each one.

They were also the first to include luminous panels stating their destination, as the line they service was effectively split in two stretches, and travellers had to switch trains at Puerta de Arganda.

Finally, they primed the "boa train" layout, but the walkable aisle only spanned two cars, while a trainset would usually carry 4 or 6.

They are extremely functional, with ample 1.3m doors and a sleek, unobtrusive design for a total capacity of 1,260 people per trainset (180 seated).

Series 9000 trains are similar to their previous incarnation, but include better accessibility for disabled people and more safety measures, such as visual and auditive warnings for the train gates and more effective emergency brakes, they also brought small aesthetic changes like the removal of the wood effect from the ceiling and the change of the red top stripe of the doors to a blue color.

The system reverses the normal circuit of the electric motors when braking, thus making the deceleration return power to the network.

The tram features a bell-like proximity warning that is activated when the train approaches a station or a level crossing with pedestrians, which has given rise to complaints from people living near the tracks because of the noise generated.

Safety features also include door activity warnings for passengers and emergency brakes comparatively more effective than in any other train dedicated to Metro service, as the trams, though remaining in their own lanes separated from other traffic, can cross roads and populated areas.

There is also a "combined" ticket, which provides for a single trip between any two points of the network except the Airport stations, which have an additional supplement of €3.

The metro is operated by its own company, under the Department of Public Works, City Planning, and Transportation of the autonomous community of Madrid.

[57] This project replaces an earlier proposal which would have instead extended the line along a semi-circular route towards Avenida de la Ilustración, via Atocha, Ascao, Arturo Soria and Chamartín.

[70][71] In November 2024, Metro Madrid announced that they had ordered 80 new trainsets from Spanish manufacturer CAF, with a total cost of about €950 million.

[73] The other half of the order consists of narrower trainsets, which will be semi-automatic and will carry a driver; these sets are destined for line .