L D Associates

Railways are continually seeking ways of maximising the capacity of their existing routes. This involves increasing the number of trains per hour whilst ensuring safety of operation. To achieve this requires a combination of train borne systems brakes, wheelslide protection (WSP), sanding systems together with appropriate signalling and train contr... ol systems and driving styles either manual or automatic as well as mitigation measures to prevent adverse weather conditions compromising the braking performance of the rolling stock. The use of automatically driven trains on metro lines has enabled an increase in service performance (trains per hour) but has highlighted the critical interdependence between the braking rates chosen for the Automatic Train Protection emergency braking, the Automatic Train Operation service brake rates (reduced, nominal and maximum) and the braking capability of the rolling stock under adverse or degraded adhesion conditions. The issue of low wheel rail adhesion, which has often been considered as primarily an Autumn leaf fall problem, can become an all year round issue if due consideration is not given to the above factors during the overall system design. The failure to adequately consider such issues at an early stage in the system specification and design can result in being unable to deliver the targeted service on a consistent basis. The need to have to reduce the service braking rate under damp, showery or drizzle conditions can seriously compromise reliable operation. The identification of relevant Adhesion Management requirements together with the design and implementation of appropriate Adhesion Management systems and measures, including both technical and operational considerations, can be crucial in ensuring that the maximum service improvements are obtained in practice. This is very important if the maximum return is to be obtained from an upgrade to a line or route. Devising such requirements benefits from a comprehensive understanding of braking, braking requirements, ...Read More