Police in Shanghai have broken up two days of protests against the extension of the city's showpiece magnetic levitation - or maglev - railway.
Shanghai's maglev train started commercial services in 2003
The demonstrations were held by residents living near the planned extension, who are concerned at the possible noise and magnetic radiation.
Shanghai authorities have already revised the route to avoid the most densely populated areas.
Super-fast Maglev trains use electric magnets to float above their tracks.
This allows for speeds substantially higher than standard railway lines, as there is no friction between the train and the track.
"The government obviously doesn't care about our welfare," one 29-year-old protester told the Reuters news agency.
The protesters are also objecting to the giant cost of the extension, which is reported to be as much as 500m yuan ($69m; £35m) per kilometre, twice as much as originally estimated.
Shanghai's current maglev line opened in 2003 and runs from the city's international airport to the financial district.
Presently the world's only commercially operating maglev service, authorities now plan to extend it across Shanghai to the city's second airport.
Although the protests were broken up by police, there were signs that Shanghai's city government is sympathetic to the protesters' concerns, despite saying the maglev line presented no health issues.
The Shanghai Environment Bureau said it had set up a phone line and e-mail address to gather "residents' proposals and opinions".
"City planning and environmental departments are very cautious and take very seriously these concerns," it added.
Last year, Germany said it had come up with the funds to launch its own maglev rail service.
The state of Bavaria is to build the high-speed railway line from Munich city centre to its airport.
The announcement sparked protests in Munich against the giant cost of the scheme.
Japan is also now actively exploring the introduction of maglev services.
The world's first commercially operating maglev railway was at Birmingham International Airport in the UK.
From 1984 to 1995, it shuttled passengers 600m from the main terminal to the nearby railway station.
But after 11 years in operation, it was hit by reliability problems and replaced by a conventional system.
Although maglev systems allow for speeds substantially higher than traditional railway lines, critics point to the much higher costs of installation.