The infrastructure systems that support our urban systems and serve citizens, society and cities, have developed over centuries. They have been variously superseded, extended and supplemented as populations have grown, technology has developed and contexts have changed. This presents challenges of maintenance (keeping the older parts going) and integration (of the new with the old) as expectations of ever better service inexorably rise. REPLENISH is focusing on the 'urban metabolism' - the flows of resources, goods and people into, around and out of cities. When the infrastructure systems underpinning this 'urban metabolism' work uninterrupted and unencumbered by excessive demand or lack of affordability, they work well and citizens are happy. This is the expectation. However there several factors combine to compromise the efficacy of these systems and materially damage citizen mental and physical health and wellbeing (H&WB): - Many infrastructure systems are not run primarily for the benefit of the citizenry they serve. Where (e.g. many utility) services are provided by private companies, their primary responsibility is to their shareholders and profit is an overriding imperative. Regulation is a mechanism for acting for the common good, but can only be invoked using incontrovertible evidence. - Our infrastructure systems are highly interdependent - a failure or need for major intervention in one will often have significant adverse consequences on many others. - Rapidly-growing demand often outstrips supply, with effects most keenly felt in mobility systems. Congestion, delays, uncertainty of travel times and plotting of routes to 'beat the competition' lead to angst and stress ('commuter rage', cf. 'road rage', in the extreme) and compromised mental health. - Infrastructure systems deteriorate with age, repeated use and due to environmental factors. Maintenance, refurbishment and replacement fails to keep pace with system-wide deterioration, causing failures and emergency repairs, and often major disruption. Disruption to the urban metabolism due to streetworks, arising from the physical interdependency of multiple buried pipes and cables beneath roads, is a prime example. - Serious side effects of current mobility systems include engine exhaust emission and airborne particulates from vehicle breaks and tyres. - Wealthier citizens can sometimes avoid such problems by using some of their wealth, whereas poorer citizens cannot. This results in H&WB inequalities. Moreover, the solution to some of these 'urban metabolism' problems offer potential for physical exercise. Non-communicable diseases (NCDs), including heart disease, stroke, cancer, diabetes and chronic lung disease, are collectively responsible for almost 70% of all deaths worldwide. Radical changes to the quality of the urban environment and the way we move around cities would manifestly improve this situation. Our infrastructure systems, as currently constituted, are therefore one of the major upstream determinants of NCDs and compromised mental H&WB, and contribute hugely to direct costs (e.g. to the NHS) and indirect costs (e.g. loss of productivity) to the UK's economy. REPLENISH contends that if our infrastructure systems and their associated cityscapes were designed with positive H&WB outcomes as the primary design criterion, huge social and economic benefits would result. REPLENISH therefore proposes, by adopting systems thinking and systems engineering (or 'doing'), to: - create the evidence base to prove the extent of the damage to citizen H&WB and the benefits of change, - rethink and redesign our engineered infrastructure systems and cityscapes, - create alternative business models that would prove the value of investment in making such change, and amended forms of governance that control their efficacy, - prove the concepts via demonstrator projects in association with the Design Council, Sustrans and other user partners.