- I will look up train ticket prices but I think that going by bus is cheaper.
- A gloomy man is going by bus and thinking his gloomy thoughts to himself.
Is the second sentence unnatural? Is it because the idiom "go by bus/train/plane" is only okay when it's used with go as gerund (as in sentence 1) or verb:
- We decided to go by bus, and we went by bus.
Or is sentence 2 really okay?