FAST to construct Riyadh Metro Line 4 extension to airport October 18, 2018 | Europe Company News The Arriyadh Development Authority (ADA), the developer of Riyadh Metro, has awarded a contract to FAST consortium to construct a 1.5-km extension (elevated) of Line 4. The extension covers two statio... This content is available to only subscribers. Username or E-mail Password Remember Me Forgot Password