https://phys.org/news/2018-09-uber-cabify-drivers-protest-madrid.html

The protest comes a day after both ride-hailing services offered one free trip per customer in Spain in an attempt to raise awareness of a months-long, sometimes violent row that has pitted them against taxis.

The conflict mirrors other rows in European countries, as taxi drivers say Uber-style competitors are threatening their livelihoods as their licences are much more expensive.