I don't have any first-hand experience, but there's a lot of data: - https://worksinprogress.co/issue/how-madrid-built-its-metro-cheaply/ - https://pedest

I don't have any first-hand experience, but there's a lot of data: - https://worksinprogress.co/issue/how-madrid-built-its-metro-cheaply/ - https://pedestrianobservations.com/2024/12/07/low-spanish-costs-are-not-about-decentralization/