# ABSTRACT There is a growing awareness among city leaders and policy-makers of the impact of the urban environment on health outcomes and inequalities. Increasingly, practitioners in built environment city departments, such as housing, planning, transport and regeneration, seek new tools and guidance to understand how their respective policies and decisions can support the creation of healthier cities. This paper presents the development of a global index to help city leaders and practitioners understand their role in delivering health outcomes through urban environment policies and programmes. The Building Research Establishment’s international [[Healthy Cities Index]] (BRE HCI) contains 10 environment categories and 58 indicators, supported by a causal pathways framework. This was achieved through an iterative process including: stakeholder engagement, evaluating research evidence, selecting indicators and identifying data sources. We tested the index and causal pathways approach on two case study cities: Dubai and London. We found that they contributed to: raising awareness of the links between the environment and health; identifying shared responsibilities and the need to work across departmental silos; and uncovering the competing demands faced by some departments (and private sector stakeholders) as they seek to deliver health promoting environments alongside other objectives. # Key takeaways - Lessons for Index Development: During the process of creating and piloting the BRE HCI we have observed a number of lessons for index development, including: ==the challenge of addressing complexity in urban health; the value of engaging stakeholders; the contested nature of composite indicators and weighting methods; the appropriateness of international comparisons of urban health; and difficulty accessing appropriate open data across global cities.== - Addressing complexity: We observed complexity as a defining feature of urban health discussed throughout the literature. The characteristics of complex urban health systems (and their sub-systems) affect how they are studied by epidemiologists, how they can be measured by indicators and how policy-makers can develop appropriate interventions. McCarney and McGahan (2015) also note the complexity of urban governance for health systems, brought on by the evolution of cities and our changing interpretation of urban health. - Stakeholder engagement: valuable for the peer-review process and weightings workshop. Engagement resulted in modifications of the methodology and strengthened the Index. Also involve govt officials and private sectors. - The problem of composite indicator: exist both sides, one that supports, and one that loathes composite indicator. The support camp looks at the angle that the temptation to refer to a single bench-mark number for comparison across other countries are irresistable, while the loathe camp said it's meaningless. Even equal weighting across categories does not help because it implies that all categories have an equal impact on health and well-being which is unlikely. The authors decided to avoid the creation of a composite indicator. - International comparisons: Media regularly report on the findings of international ranking such as Arcadis Sustainable Cities Index and the Mercer Quality of Living Survey. Such articles focus on positioning in the rankings, prompting attention from politicians who see their cities as competing for investment and talent on a global scale. Academic peer reviewers were strongly opposed to ranking cities. The rationale was based on: - The inappropriateness of comparing cities with different health and environment contexts - Limitations with available data - Weaknesses in the evidence base for some exposures, particularly in relation to low and middle income countries - Lack of appropriate method to combine and weight categories or indicators - Potential for unsuitable policy responses as a result of such comparisons. - Limitations and further research: “We concluded that despite the potential advantages of producing a composite indicator and ranking this measure (see Saisana and Tarantola 2002), the BRE HCI would be more valuable as a tool to compare category scores or individual indicators.” (Pineo et al., 2018, p. 39) # Overall value of BRE HCI 1. Increase awareness of the multiple urban environment exposures which lead to health impacts 2. BRE Casual Pathways Framework creates a simple starting point for discussion about local challenges, policy interventions, and monitoring mechanisms. 3. Provide a useful starting point toward a standard set of urban health indicators which could be used globally