When I used to ride Caltrain to/from work, I would often have an uninterrupted stretch of 45+ minutes in a cozy single seat (I would always take an upper deck seat in the "gallery" car) to either doze off or use this time to focus on something. I would get so much done on those days if I managed to avoid the sun blasting too much sunlight on my screen/seat. This commuter rail experience is probably familiar to many of us, but it's specific to commuter rail - being a passenger on a subway or in a car/bus is too chaotic or bumpy to do this.

More generally, I find that switching up your surroundings is absolutely vital for your brain's ability to focus on hard tasks. I will hit a wall if I try to work multiple 10+ hour days sitting in one spot, but a comfortable spot in a different coffee shop or lounge can totally trick my brain into powering through.