alt Hacker NewsBecause it’s a slightly different argument. “More people will use the highway” is not really applicable here. The bus analogy also didn’t meant “more people will take a bus”, just that if you have bus route where 20 people on each bus stop need to wait for the next bus, if you increase capacity of buses by 10, then only 10 people will be waiting on bus stops, but you will still have 100% bus utilization.
In other words, with added lane on highways, it’s sociological mechanism, which is slightly less precise analogy.
If you run the same bus route and frequency, one day with buses that fit 50 people and have 100% utilization, and the next day with buses that fit 100 people and have 100% utilization, you transported twice as many people on the second day as on the first day
This implies that on the first day a lot of people either didn't make their trip because there was no space, or took a different mode of transport. Presumably mostly the latter. With the highway example the same is true, just that it will be mostly people not making the trip at all before the capacity improvement because they were unwilling to make the higher time commitment