NR SSIDIS177 ISSUE 6 PDF

INTRODUCTION

This paper has been prepared to define the SSI data required to interface to an MCB level crossing fitted with obstacle detection systems (MCB-OD). MCB-OD has been developed as an alternative solution to the traditional MCB-CCTV. Operation of an MCB-OD level crossing is intended to be fully automatic, with complete road-rail protection provided by 2 or 4 barriers. The purpose of the Obstacle Detection (OD) system is to guarantee that the crossing area is clear of all obstructions, both during the barrier lower sequence and also once the barriers are confirmed to be fully lowered; under normal operation the detection system also allows the automatic declaration of the crossing clear condition. For a level crossing that would otherwise have been categorised as a MCB-CCTV crossing, the use of detection systems provides a means of reducing signallers’ work load, allowing larger areas to be operated by one signaller. MCB–OD crossings will be fitted with two separate obstacle detection systems:

1. A Primary Obstacle Detector (POD) which is a radar detector system

2. A Complementary Obstacle Detector (COD) which is a LIDAR (laser) detector system.

Where required, an additional Barrier Obstruction Detector (BOD) may be fitted where there is a risk that vehicles may stop under the barriers.

For MCB-OD crossings, the Signaller is not provided with monitors to observe the operation of the crossing. A local CCTV system is provided, but this is only used for incident recording, and is not provided for any other purpose than recording the day-to-day operation of the crossing.

All MCB-OD crossings will have two Local Crossing Units. One (the LCU) is for emergency only, as it by-passes the level crossing’s relay locking. The second local Level Crossing Unit (the XCU) is placed alongside the LCU, and incorporates a local “crossing clear” functionality. This allows an on-site operator with a direct view of the crossing to override the obstacle detector systems and declare the crossing clear, allowing signalled moves to take place over the level crossing.

Details of the object detector application are detailed within the MCB-OD Functional Requirements Specification [Ref. 4], which should be read in conjunction with the typical circuits for MCB-OD [Ref. 3]

The interface between the interlocking and the level crossing circuits is as defined in the MCB-OD typical circuits [Ref. 3], except that the interlocking functions are carried out in SSI data rather than by relays. MCB-OD controls and indications may be transmitted between the Control Centre and the crossing either by a separate TDM system, or through the SSI.

The data in sections 5, 6, 7 and 8 is NOT required where the controls and indications are transmitted via a TDM system. The data in section 9 is always required, whether the controls and indications are transmitted via the SSI or via a TDM system.

Where transmission of the controls and indications is via the SSI, the data in sections 5 and 7 should be used with a VDU control system, or the data in sections 6 and 8 with a panel.