This is vastly dependent on country. And even area within the country. To a large extent I guess population density.

E.g. come to London. Take a train heading as far as possible out of town. With every stop, the "average face" will soften, you'll start seeing smiles. Then eye contact will become "acceptable". You may find people greeting you eventually.

Time of day/week also makes a huge difference. The overcrowded commuter trains are awful. Except Friday afternoon, when the atmosphere at least on the long distance commuter trains out of London tends to be completely different.

Or go to Paris, and people will be far more open to eye contact from the outset.