Keeping the railways safe will be less expensive from now on. Dutch rail infrastructure manager ProRail has just approved PLC Interlocking for use throughout the Netherlands. The system was (previously known as Eurolocking) was developed by Movares, in partnership with Dutch rail infrastructure provider ProRail. Jean Paul van Hengstum manages the PLC Interlocking programme for Movares: ‘ProRail approval marks a breakthrough in train protection. It uses off-the-shelf components from the process industry, which means that in future it will be possible to build railway safety systems faster and, above all, more cheaply.’

He continued: ‘As is often the case with innovation, the original idea for PLC Interlocking was simple: replace expensive, bespoke interlocking computers with off-the-shelf units that were already on the market. We’re using PLCs, or programmable logic controllers, which are microprocessors designed for controlling processes. They’re are widely used in the process and chemical industries. We looked at whether they could be used in the railway environment, and discovered that PLCs were ideally suited for use in railway interlockings. Not just in the Netherlands, but all over the world.

Pilot project

A successful pilot project using PLC Interlocking has been running since 2012, with the system working perfectly on a passenger line at Santpoort Noord station. PLC Interlocking is now being installed at Beverwijk. Van Hengstum continued: ‘PLC Interlocking has many fields of application, in addition to heavy rail, such as light rail, level crossings, sorting sidings and rolling stock transfers.’

Train protection

There is a clear separation in the Netherlands between how trains are controlled and how signals and points are controlled. The two are known as the ‘control layer’ and the ‘interlocking layer’ respectively. In the control layer, routes are set up and requests generated for signals and points to be placed in a given state, so the driver can use the route. In the interlocking layer, these requests are verified and the points and signals are placed in states that are guaranteed to be safe. The interlocking system prevents collisions between trains, derailments, and collisions between trains and vehicles at level crossings. So the interlocking plays a critical role in keeping the Dutch railways safe. Currently, interlockings consist of specially designed safety computers or complex systems consisting entirely of what are called B relays. B relays are extremely safe, but they are also rather dated and they do have technical limitations. Safety computers are comparatively expensive, as they can only be used for a narrow range of applications.

There is an acute need for a new train protection system in the Netherlands. Some 15 percent of existing interlockings will have to be replaced over the coming ten years. Currently, a good eighty percent of the Dutch rail network is equipped with conventional relay interlockings.


Further details:

Jean-Paul van Hengstum
Programme manager
T: +31 30 265 3171
M: + 31 6 57 622 464

Press release Eurolocking
2013 – 01 – 28

Come and find out more about Eurolocking at Rail-Tech on 19 March at the Movares stand no. F008.