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Structural Health Monitoring (SHM) has an important role in the management of transport infrastructure. However, most SHM techniques are based on data obtained from dense networks of point-based sensors (rather than sparse networks of spatial sensors) and so, in relative terms, they are costly to implement. Furthermore, most commercially available strain sensors have a limited maximum range - typically 1% to 2% - and are not well-suited to providing information of a severe loss of structural integrity (following eg an earthquake). The SENSKIN project develops a dielectric-elastomer and micro-electronics-based skin-like sensor, based on the use of a large highly extensible capacitance sensing membrane and advanced micro-electronic circuitry, for monitoring transport infrastructure - such as bridges. The sensor will provide spatial measurements of strain of more than 10% and is being designed to (a) require low power to operate, (b) be easy to install (c) have a comparable or lower cost than conventional strain sensors, (d) allow simple signal processing, and (e) have the ability to self-monitor and self-report. The system will support the new and emerging technology of Delay/Disruption-Tolerant Networking to secure that strain measurements acquired will reach the base station even under extreme conditions where communications may be disrupted. SENSKIN also includes the development of a Decision-Support-System (DSS) for (a) proactive condition-based structural interventions under normal operating conditions, (b) reactive emergency intervention following an extreme event. In assessing potential rehabilitation options, the DSS will use the data supplied by the SENSKIN sensors (and, potentially, supplementary/secondary instruments) together with advanced structural analysis models, whilst taking account of the lifecycle economic, social and environmental implications. The new sensor will undergo laboratory calibration and environmental tests using small and large steel and concrete specimens. The overall monitoring system will be evaluated and benchmarked on actual bridges of Egnatia Highway (Greece) and Bosporus Bridge (Turkey). This paper describes the concept and principles of the SENSKIN sensing system, and its various components. Particular attention is given to end-user requirements and how these relate to the specification and architecture of the system.