The OCCASION project brings together the University of Southampton's expertise in railway simulation and control (Transportation Research Group) with more generic expertise in operational research (Centre for Operational Research, Management Science and Information Systems). This project will identify and assess innovative approaches to overcoming nodal capacity constraints by examining the scope for technological improvements and operational changes. Although the emphasis is on modelling, it will also cover technological and operational issues. This will include examination of incremental changes, such as improved design of points, changes in signal spacing and overlaps, but also more radical changes including concepts from other modes (e.g. intelligent speed adaptation) and a relaxation of the Rules of the Route/Plan. We will adopt a layered approach by examining nodes of increasing complexity on the South West Main Line before developing a detailed case study of Reading station and its approaches. Our methodology will consist of four main elements. Firstly, we will provide a state of the art review which will examine how nodal capacity problems have been tackled to date in Britain and overseas. We will also examine systematic approaches to innovative problem solving, as proposed by the TRIZ methodology and general systems theory. Second, we will develop a generic meso-level model and simulation tool, based on RailSys, which will determine train routeings and schedules, levels of disruption and reactionary delay and measures of capacity utilisation at nodes. Third, we will develop a micro-level optimisation by applying production scheduling techniques to rail scheduling, and by specifically investigating shifting bottleneck procedures and local search approaches. Fourth, we will integrate the simulation and optimisation models by using a multi-commodity integer programming formulation to examine cost versus service quality trade-offs, using techniques we have previously applied to rail freight. This will be used to determine the most effective technological solutions (including enhancements to signalling, switches and crossings) and operational solutions (including dynamic traffic management). In undertaking this work, we will be assisted by our industrial partners, Arup (operations) and Balfour Beatty Rail (technology). Arup will also use the Legion simulation model to determine the extent that pedestrian movements within the station may constrain the scheduling of trains through the station. Our key outputs will be prototype software tools that will assess the extent to which nodal capacity can be increased. This could be subsequently applied to other bottlenecks on the National Rail network. An advice guide would also be produced on measures to overcome capacity constraints at nodes.