Safety and Reliability
The overall safety process of the VECTUS system follows the standard EN 50126/IEC62278 "Railway applications – specification and demonstration of Reliability, Availability, Maintainability and Safety (RAMS)". This is a standard which is recognised throughout the world.
Safety considerations have been an integral part of the development of the VECTUS system over the past ten years. The safety work has consisted of various activities, such as developing safety plans and performing safety audits, safety analysis, FMECA (Failure Mode Effect and Criticality Analysis) and fault trees in order to establish a complete safety case. The overall safety targets have been verified for a generic system by performing a Quantitative Risk Assessment (QRA). The QRA includes 78 different sensitivity parameters to verify the criticality of different input factors. For a larger system, passenger risk was quantified to 0.165 fatalities per billion person kilometres, meaning that the VECTUS system’s standards are as high as, or higher than, the current performance of railway systems and metros in Western Europe.
The RAMS perspective for the VECTUS system is to keep the maintenance intervals as long as possible and to reduce the number of components that need to be replaced on a regular basis. For a system using in-track linear induction motors, there are no regular maintenance-intensive parts or systems such as gearboxes, rotating motors or current collection systems. For a system with on-board propulsion, a low current collection system is necessary. A DC bus distribution, with fairly small supply stations, is used. These are typically co-located with the passenger stations to ensure only small distribution losses are incurred during high power needs such as during acceleration.
Based on the RAMS analysis, redundancies and backup systems have been introduced to maximise the availability of the system. The dynamic control system will automatically re-route vehicles in case of congestion or breakdowns. It will also allow vehicles to reverse direction in order to clear and re-route a track segment around problems which cannot be resolved within a reasonable time. It is possible to deal with most vehicle failures by on-board backup systems, or by short term operation in reduced performance modes, until repairs can be made in the workshop. Vehicles can push other vehicles in front of them to the nearest station. Alternatively, special service and rescue vehicles can be deployed if required.
A life-cycle cost (LCC) model for a generic system has been developed. Parameters can be chosen for system size, operational hours, mileage, cost of labour, energy, etc. It uses the RAMS analysis combined with spare-part prices as input for all corrective maintenance. It also contains the actual maintenance plan, with prices for consumables, as a basis for the planned maintenance together with an estimation for other tasks such as cleaning.