Is it permissible to trade in means of transportation where men and women intermix, knowing that segregation between them is not possible in the country's culture?

There is no harm in working or trading in small or large transportation vehicles, because transportation is a permissible benefit. As for the mistakes committed by passengers, such as immodest display (tabarruj) or unlawful mixing (ikhtilat), their sin is upon them. The vehicle owner should advise, enjoin good, and forbid evil to the best of their ability, knowing that the gathering of both sexes in a vehicle does not necessarily imply unlawful mixing.