gitmeshiga,
Au contraire, R’Moshe teshuva, regarding riding packed buses or trains where touching members of opposite gender are inevitable, makes much more sense if you understand “derech chiba” to be objective.
Buses and the like involve bodies pressing together with a much greater likelihood of hirhur than a handshake. Af al pi ken, because on buses it is clear (to the objective onlooker) that the touching is not intentional, it is still mutar according to Reb Moshe. Ma shen kein, according to Rav Shachter and Rav Berkowitz it should depend on the attractiveness of the people on the bus and the self assessment of the individual.