Austria on Wednesday raised the speed limit to 140km/h from 130 km/h on two stretches of one of the country's main motorways.
The higher speed limit, introduced by Transport Minister Norbert Hofer of the far-right Freedom Party (FPOe), is widely seen as an attempt to woo motorists.
By increasing their speed on the 60km of affected motorway, drivers reportedly stand to save two minutes travelling from the capital Vienna and the western city of Salzburg.
The trial will run for a year.
Opposition parties, green activists and others have criticised the move, citing an increased danger of accidents and higher environmental pollution.
Hofer has said motorways and cars have improved, so it's time to test if the speed limit can be raised.
He tweeted last week when announcing the change: "We are building motorways, not 'slow roads'".
In neighbouring Germany, known for its no-speed-limit motorways, the average speed comes down to around 120km/h around cities and road works.