[3] Having a semi-metro alignment, it runs underground in central Porto and above ground into the city's suburbs while using low-floor tram vehicles.

It currently has a total of 85 operational stations across 70 kilometres (43 mi) of double track commercial line.

[8] During the 1990s, political leaders started advocating for a partially underground electrified railway transport system to service the city of Porto and the surrounding municipalities.

The remaining section between Pedras Rubras and Póvoa de Varzim was opened a year later in March 2006.

[11][12] In July 2017, an infill station called VC Fashion Outlet - Modivas [pt] was added.

In the northern end, the São João Hospital and IPO stations, were not brought into service until March 2006 due to safety concerns[citation needed].

In the southern end, the line was expanded until D. João II [pt] in May 2008 and then to Santo Ovídio in October 2011.

[9] In June 2024, the line was extended southwards by 3.15km with three new stations added, Manuel Leão, Hospital Santos Silva and Vila d'Este.

On the supply side, the number of yearly train trips has varied, and as of 2023 it had not recovered to the peak of 370,000 in 2019.

They also have more seats, and can, in common with most modern light rail systems, recover 30% of the total of consumed energy during braking.

The Flexity Swift consists of three components linked by articulations, with a capacity of 100 seated and 148 standing passengers.

Under this system, a ticket holder can use multiple modes of transportation by various providers within a certain time period.

They are free for students between the ages of 4 and 18 and discounts exist for families, seniors, veterans and lower income households.

Between Trindade and Estádio do Dragão stations it uses a new tunneled alignment, whilst between Senhora da Hora and Senhor de Matosinhos stations it mostly uses a new surface alignment, albeit with short sections coinciding with the route of the Matosinhos branch railway.

[2][32] Although no extensions are planned, consideration was given to use the abandoned Famalicão branch of the old Póvoa Line, converted to a cycle path after closure, to reach Mourões and Barreiros, near Avenida 25 de Abril.

While, this project was never pursued, the Porto Metro provides a bus link between the ISMAI and Trofa.

[14][2][34][35]Line D or the Yellow Line runs between Vila d'Este and Hospital São João stations, with 17 intermediate stations and a very visible crossing of the River Douro on the upper level of the iconic Dom Luís I bridge.

[2] As of 2023, it was the busiest line of the Porto Metro, transporting a total of 30 million passengers across 106,500 train trips throughout the year.

Half of the trams have a southern terminus at Santo Ovídio, thus frequency is halves in the rest of the line until Vila d'Este.

Depending on day and time, between one and three trams an hour continue beyond Trindade to Estádio do Dragão, serving a further four intermediate stations and taking about 10 more minutes.

[2][37] Line E was specifically built to serve Porto Airport, and Aeroporto station is directly accessible from the terminal building.

[38][39] Besides the shared segment between Senhora da Hora and Estádio do Dragão, Line F runs mainly above ground.