> "Something Beijing lacks are express lines." Honestly, if I had to come up with just one innovation that has shaped NYC the most, it has to be the 4-track su

> "Something Beijing lacks are express lines." Honestly, if I had to come up with just one innovation that has shaped NYC the most, it has to be the 4-track subway. It not only gets you around faster but makes the system enormously more resilient to outages and anomalies. The fact that the subways are 4-track has shaped Manhattan and the outer boroughs in amazing ways. All the more disappointing all the new construction will be traditional 2-track :(