The use of outsourced logistics services is currently quite significant and still increasing worldwide, which gives logistics service providers a great opportunity to make more profit while at the same time confronting them with fiercer competition than ever before. According to the Thirteenth Annual (2008) Third-Party Logistics Study, domestic transportation has turned out to be the most frequently outsourced activity that mainly includes forward distribution and reverse collection. Therefore, the main goal of this study is to develop innovative routing strategies that optimally integrate forward distribution and reverse collection to help logistics service providers reduce their operating costs and thereby enhance their market competitive power to reap additional profits.