Public transport workers and their supporters began a 24-hour strike on Tuesday in Madrid.
Around 500 attended a protest outside City Hall, bringing a range of signs, flags and banners.
The action coincided with the 25th Conference of the Parties (COP), currently being held in the capital.
Unions representing employees of Madrid's Empresa Municipal de Transportes are demanding more drivers be... Еще hired to improve the service. They also criticised the privatisation of certain services such as the 'Christmas light bus', with the contract awarded to ALSA by a City Hall controlled by a coalition of the Partido Popular (PP), Ciudadanos and the far-right VOX party.