To lower Life Cycle Costs (LCC) of main line interlockings, the Dutch Railway Infrastructure Manager Pro- Rail follows the strategy of an open technology and market approach. A newly developed interlocking based on standard “Commercial Off The Shelf” (COTS) hardware is a fullfledged alternative for existing main line interlockings. The engineering, commissioning, modification and maintenance can be executed by at least two market participants. The PLC interlocking is the first Programmable Logic Controller (PLC) based main line interlocking meeting the requirements of the highest safety level (Safety Integrity Level 4). ProRail has commissioned its first PLC interlocking at the Santpoort Noord station and has reached type approval in December 2012.