Madrid's City Hall has brought in a series of new measures aimed at tackling pollution in the Spanish capital, including limiting the amount of traffic in the city centre and lowering speed limits at times of high pollution.
In 2015 Madrid exceeded the highest nitrogen dioxide levels permitted by the European Union for the sixth year in a row.
Nitrogen oxide (NO2) - a toxic substance emitted by diesel car engines - can affect the respiratory and cardiovascular system and Spain, which recently received the dubious honour of becoming the "most polluted country in Europe", is urgently trying to tackle its soaring pollution levels.
The new protocol aims to address the city's high levels of NO2 by introducing a series of new measures, on top of those brought in by the city's previous conservative Popular Party council.
Nuevo Protocolo de medidas en situaciones de alta contaminación pic.twitter.com/8csWN6edUw— EMT de Madrid (@EMTmadrid) February 1, 2016
Madrid's public bus company tweeted the new measures on Monday.
The new protocol, which comes into force on Monday, includes four levels of alert: prior warning, warning and alert.
The prior warning level will be activated when two monitoring stations in the same area measure more than 180 micrograms of NO2 per cubic metre during two consecutive hours.
The highest level - alert - will be issued if two monitoring stations in the same area of the city measure 400mg of NO2 during three consecutive hours.
Measures to tackle the high levels of NO2 include lowering the speed limit on the M-40 motorway leading into Madrid to 70km/hour.
If NO2 levels exceed the prior warning level for two consecutive days, parking metres will be disconnected in the city, banning all non-locals from parking in the centre of Madrid.
City Hall has confirmed that in "exceptional" circumstances all vehicles will be banned from the city centre.
Locals will be given one day to arrange alternative travel arrangements before the protocol will come into force.
City Hall will contact locals through local media, as well as on social media and big screens in bus and metro terminals.
In November, City Hall announced emergency measures to tackle the dangerous level of pollution in the city, which included temporarily banning vehicles from parking in the city centre.
Madrid's 3,954 parking metres were all deactivated (below) and commuters were encouraged to take public transport.
Photo: Jessica Jones
It was the first time the pollution protocol brought in in March 2015 by former mayor Ana Botella had been put into action.
The new measures are hoped to further tackle the pollution problem in the Spanish capital and mirror various other schemes adopted in cities around Europe.
In January, authorities in Stuttgart, Germany encouraged locals to leave their cars at home as pollution levels in the city soared, while in Italy cars were banned from the roads of Milan and Rome in December after smog smothered the cities.