Key points from article :
Musk clarified that, though he has shared images of vast Martian cities in his presentations on Mars colonization SpaceX isn’t focused on building those cities itself.
They are aiming to build the equivalent of the transcontinental railway.
Musk also reiterated previous claims that SpaceX is designing the new Mars rocket – still code-named BFR which stands to be as safe and reliable as today’s commercial airliners.
Its first scheduled flight will be in 2022.