Service tax liability for goods transporter

There is a goods transport agent providing taxable service in respect of transport of goods by road. He does not own any truck but he only acts as an agent between truck owner and service receiver (consignor or consignee) and receives commission for the service provided by him. So is he liable to pay service tax ???  in case of goods transport agency it is the service receiver who is liable to pay service tax so whether there is any option available to the service provider (goods transport agent) to pay service tax himself ?