People like to claim that "cars are flexible." And the claim has some truth. But the whole truth is not so simple.
Cars require an extraordinary amount of terrestrial space. They are extremely inefficient in terms of landuse. People who attempt to drive in urban areas are faced this this problem every day. Because "cars" require so much space, they become immobilized when travel demand is high. And when they are "immobilized," or stuck in traffic, they are inflexible and extremely inefficient. Cars are most efficient in terms of space when traveling at relatively SLOW speeds. The myth of "flexibility" is exposed.
Public transportation, especially rail transport, is inherently efficient in terms of space. Rail has the "flexibility" to transport far more people at HIGHER SPEEDS than "cars." Public transportation is flexible in terms of capacity and speed.
IMAGINE if we treated roadways the same way we approach Public Transportation. When a scheduled bus or train is operating under 10% capacity, detractors of public transportation claim that it is "too expensive," and service needs to be reduced. The more infrequent and inconvenient public transportation becomes, fewer people ride it.
NOW, let's use the same approach to roadways! Most residential streets and rural roads "operate" WELL BELOW 10% capacity! Once we eliminate those feeder roads and rural highways, most drivers will not be able to access major corridors. As driving is reduced, eventually all roadways will be eliminated.
We need all modes of transport. Each mode, highway, rail, aviation and waterway transport can provide an important role in creating mobility. But we fail to use each mode to meet the demands each can best meet, and our transportation system fails.
I find it ironic that so many of the "improvements" made or sought in highway transport (metered freeway access, hybrid and electric vehicles, self-driving vehicles, intelligent highways, multiple trailer trucks) are characteristics that have long been, or easily incorporated, in railway transport. The bottom line: we are expending much effort to make roadways perform more like rail transport. There is a MUCH easier and faster way to implement these improvements: Increased investment and reliance upon railway transport!!!