2013 – March – Wullems – How safe is safe enough? A Socio-technical View of Low-cost Level Crossing Safety

Christian Wullems BIT(Hons) PhD MIEEE MACS Cooperative Research Centre for Rail Innovation George Nikandros BE CPEng FIRSE MIEAust MACS (Snr) Australian Safety Critical Systems Association Peter Nelson-Furnell B.Bus(Transport) Public Transport Victoria Low-cost level crossings are often criticised as being unsafe. Does a SIL (safety integrity level) rating make the railway crossing any safer? This paper discusses how a supporting argument might be made for low- cost level crossing warning devices with lower levels of safety integrity and issues such as risk tolerability and derivation of tolerable hazard rates for system-level hazards. As part of the design of such systems according to fail-safe principles, the paper considers the assumptions around the pre-defined safe states of existing warning devices and how human factors issues around such states can give rise to additional hazards.