Designing a mile-high skyscraper will need non-conventional technology and efficiency in building tall skyscrapers. Additives like whisker-thin steel fibers are enhancing concrete's strength and rigidity. Smart fibers and carbon nanotubes, when added to concrete, will increase compression beyond 200MPa. There are also advances in elevator systems, such as traffic management algorithm that optimizes pickups and drop-offs by grouping passengers according to the floors they select and multiple elevator cars that travel in the same shaft. In terms of power, photovoltaic and wind turbines are being developed to avoid using power from the grid. In safety terms, current codes mandate that buildings include flame-, smoke-, chemical- and gas-resistant refuge floors.