A problem in long tunnels, is that accidents brings nightmare scenarios [1]. This is one of the reasons why cars are loaded on trains in the Eurotunnel. I also

A problem in long tunnels, is that accidents brings nightmare scenarios [1]. This is one of the reasons why cars are loaded on trains in the Eurotunnel. I also hope they do proper traffic simulations that take into account the Braess’ paradox. My guess is that there are probably a host of other lower hanging fruits they may be able to take to reduce traffic before boring tunnels. One such thing is parking space markets, you wouldn't know, but a lot of the traffic in congested cities is actually caused by cars looking for parking. Furthermore, In NYC, I believe traffic could be significantly reduced by simply enforcing violations for cars blocking intersections. At rush hours, some intersections on the roads leading to bridges and tunnels are constantly blocked by cars, trucks, buses etc. A lot of the traffic can also be reduced by developing smarter traffic grids, where lights are not simply programmed on time intervals. And developing the unrealized potential of friendlier cities for bike. In a lot of these ideas, the problems are not necessarily technical but rather governance. Finally, self-driving cars will allow better carpooling and car-sharing. [1] https://en.wikipedia.org/wiki/Mont_Blanc_Tunnel#The_1999_fire https://en.wikipedia.org/wiki/Mont_Blanc_Tunnel#The_1999_fir...