Urban Transit Guides Application of Advanced Train Control

North American railway authorities are concerned about the introduction of processor‐based equipment, which often does not fit existing rules, into vital or fail‐safe functions. This situation has already been faced in the railway industry abroad, where processor‐based controls are steadily being introduced, particularly for intersection interlocking and control. Urban rail's safe use of these systems offers a valuable guide to their introduction to railways. The urban transit industry has of necessity more complex train‐control systems than most railways; and in both North America and abroad the industry has introduced complex train‐control systems that frequently involve processor‐based decision making and associated vital software. Several current train‐control systems, some of which operate trains without drivers, are fully processor‐based. Most rail systems with rolling stock, train‐control, or vital subsystems using software‐based processors have implemented a safety‐assurance plan or its equivalent. These plans usually examine the entire system, including software safety assurance. The operator will normally accept documentation from a supplier's systems‐safety assurance plan. The plan will invariably audit suppliers' design and assurance processes and produce a paper trail that goes back to the initial design work.