Are all railway sleepers treated?

Not all railway sleepers are treated, most reclaimed sleepers at some point in their lives have been treated and sometimes not with very pleasant products. Softwood sleepers are generally pressure treated to improve their life span, and some cheaper softwood sleepers are dipped in preservative, but this is not such a successful method. Oak sleepers are generally not treated but we would recommend some level of treatment for any sleepers even oak that are going to come in contact with the ground