From the article:
Just like the US highway infrastructure, Tor needs new bridges. Tor bridges are computers that act as hidden gateways to Tor’s darknet of relays. After campaigning successfully last year to get more volunteers to run obfuscated Tor bridges to support users in Iran trying to evade state monitoring, the network has lost most of those bridges, according to a message to the Tor relays mailing list by Tor volunteer George Kadiankakis.
- Press Clip