Now Boring Tunnels belong here because they requires EVs and they could be an incredible enabler of EVS. Can't practically have a tail pipe in the tunnels even as some underwater tunnels have enabled that you'll notice their astronomical cost- and of course tail pipes in tunnels have added to the cost of construction- so green tunnels are cheaper on that front too. Of course the people at Boring have thought of these things but maybe others have something they haven't. I haven't seen what follows mentioned in the press, but I've seen a lot of concern about accidents and failures and bottle-necking from edge cases in comments. 1. Presumably the Tesla system and that of other cars would pre certify use of the tunnel before entrance by a diagnostics check. And presumably this actually adds merit to a vertical drop elevator at both entrance and exit as a way to make sure that no cars get in that don't pass and yet getting rid of such elevators any way possible could reduce cost further and increase reliability. Is the Tesla system like a magna steer system(?) you really would want to disable any mechanical linkage while in the tunnel under AP unless you could be sure the coasters could overcome inadvertent or even misguided intentional steering input. 2. It seems the best and most reliable situation for coasters would be for the coasters to generally not make contacts and rely on the autopilot to guide at tight tolerance. This of course could create a stability situation if they did make contact. I wonder proper channeling of air by coaster fairings or air guides could create the air hockey effect and help prevent contact and help slot the vehicle at speed- the issue is probably more at speed so aero dynamic guides might help. 3. When there is a flat or failure (much less likely in an EV) I could see compact units running between the rails that seem to be in the tunnels running under the cars coming to jack up the car and take them to an elevator. This has the advantage of being able to run under traffic but when it gets to an elevator there will need to be a mechanism to push a car onto the elevator if need be and one to push it off the elevator into an emergency space or even spaces to free up the elevator again for both input and output. Also it would seem necessary to have the pedestrian cars and or special forklift cars that could fork lift front and back other vehicles at times. Also may be necessary to have regular pit stop pull offs if necessary for logistics but these types of arrangements may present some risks in they are breaks in the continuity of the channel? Because of the need to think through the logistics (which be improved as need be even after the system is put in place) it almost seems like it has the issues of launching bullets through long barrels. Gatling gun type dynamics. So many offshoots and axis points to attend to logistics in real time seem needed and this pushes cost but the pay off is huge. Fool think is always trying to drive growth but they need to understand that ain't happening if traffic is a choke point. Bezo's idea for the doing all manufacturing on the moon and taking the logistical traffic vertical would help quite a bit but they have to understand that their fool growth for the sake of growth (bs that supports money for the sake of money unfortunately- but getting these fools in line can be helpful) is infeasible unless you go vertical above and below ground with tunnels and drones and autonomous vehicles- even eliminating stop lights and with drones and with a green revolution. This is not a maybe this is a necessity even against issues like urban sprawl their little cities must flow with the techniques applied to CPU design and at some point soon with a quantum computer factoring the Hamiltonians in real time an freight flow into a city and optimum placement of freight units within where house stacks arriving at some sort of macro super fluidity for all things that travel. This is not a maybe this is a necessity unless they want to be road kill for new green economies like China that are not built out and won't do this. Don't do it then have fun learning Mandarin in middle age. *Finally wonder if magnet spacers might work but be cost prohibitive even if the magnets built into the side walls were far apart. Any of this would add cost and rare earth could be cost prohibitive and un-powered magnets could run down with time- thinking maybe combo of coaster aero fairings and cheaper non rare earth magnets could be circuited together in a manner such that the vehicle at speed built a field just ahead of the vehicle that would form a strong positioning/tracking force. I wonder about the slotting or vertical tracking of such fields as the friction of actual coasters might be superior. A big downside to such a system is that it presumably adds cost and fail points to the tunnel that coasters don't as you move in the direction of mag lev. But coasters create wear and tear as well and reliability issues. If vertical movement is a concern with the regard to such coasters maybe a generally passive tail hook relative to the lower rails- probably not.