I think the combination of driverless trains and automated platform screen doors is the gold-standard for new metro-like systems. The new REM in Montréal is able to have very high frequencies with much lower cost, so transit users should be able to get more transit for the same cost and the municipality isn't worried about the burden of high operating costs for the next century. The platform screen doors are great too, anyone who's taken the Metro enough has had to wait for hours because someone has fallen onto or committed suicide on the track, which feels like such a sad problem to have when the solution exists.