Madrid may be about to become the first European city to scrap a major urban low-emissions zone after regional polls left a rightwing politician who views 3am traffic jams as part of the city’s cultural identity on the cusp of power.

Isabel Díaz Ayuso, who is expected to become the new Popular party (PP) president of the Madrid region, believes night-time congestion makes the city special and has pledged to reverse a project known as Madrid Central, which has dramatically cut urban pollution.

The PP’s mayor-in-waiting, José Luis Martínez-Almeida, under whose remit the scheme falls, vowed that his first action would be to “address” Madrid Central. “It was one of the pillars of our campaign,” he said. The PP would instead prioritise street cleanliness and conservation, he added.

During the election campaign, Ayuso told El Pais: “I do not think [traffic jams] are a reason for enjoyment but it is a sign [of the] identity of our city, that the street is always alive.”

Congestion is “part of the life in Madrid”, she said, adding that the city’s nightlife “goes hand in hand with traffic jams”.

A reversal of the popular Madrid Central system would mark the first time a major European city had turned the clock back on clean air reform. The scheme has attracted the ire of conservatives as a totem of the outgoing Mas Madrid movement and its leftwing leader, Manuela Carmena.

Greeting the election result on Sunday, Javier Ortega Smith, the secretary-general of Vox, the PP’s prospective far-right coalition partner, said: “Starting tomorrow, Madrid Central is over.”

An estimated 30,000 Spaniards die each year due to air pollution, according to the European Environment Agency.

Within a month of its launch last November, Madrid Central had cut urban traffic by up to 24% and nitrogen oxide (NOx) levels by 38%. CO2 emissions also fell by 14%.

Pollution tests around the city’s central Plaza del Carmen station last month found that nitrogen dioxide (NO2) levels had plunged by almost 50% compared to 2018, reaching their lowest point since 2012.

Nuria Blázquez-Sánchez, a spokeswoman for the Ecologists in Action campaign group, said: “Madrid Central has improved air quality even more than expected. City centre residents are happy with the LEZ [low-emissions zone] and voted massively for Manuela Carmena.

“Reversing such a successful project will have severe consequences for public health, particularly the health of vulnerable people like children, pregnant women and the elderly.”

Carmena is a popular figure and Mas Madrid emerged the largest single party from the polls, but without a governing majority.

The centre-right Ciudadanos says it will not talk to Vox, but is thought likely to join a de facto coalition if an accommodation between the extreme right party and the PP emerges from post-election haggling.

Even then, dismantling Madrid Central may be a complicated affair, with environmentalists mounting a rearguard defence of the pollution measure in the city council and courts of law.

The LEZ was introduced after the European commission threatened Spain with legal action unless it complied with the air quality directive.