Slavery and public transport Some societies that excelled at collecting slaves found that they actually had too many for the available jobs. As there is no point in feeding and housing unemployed slaves, they began to capitalize on their competitive advantage by selling the excess to other societies. This involved moving the slaves to the slave markets and eventually to wherever they could slave for their new owners. Slaves were sometimes transported over considerable distances and their owners did not want excessive wastage in transport. They convinced the rulers that public transport should be provided for the slaves. So, barges, galleys, wagons and sledges replaced the walking and swimming that had previously been necessary. It was once thought that modern public transport had evolved