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There has been a recent surge of research interest in quantifying the health and environmental impacts of increased cycling in urban environments. Although there is general agreement that the benefits of increased cycling outweigh the risks, most of the methodologies developed have had limited value for evaluating real-world transport policies. This is because they are based on hypothetical scenarios where increased cycling takes place but give no consideration to the courses of action which may help policymakers to achieve the scenarios. A useful extension to these methodologies would be one which allowed a user to find the optimal infrastructure design and/or policies which would maximize total societal benefit, taking into account the health and environmental impacts of cycling. In this study, a Network Design Problem is formulated for systematically designing cycling network layouts in order to maximize the net benefits to the network users and society. The problem is formulated as a mathematical program with equilibrium constraints (MPEC) and a solution approach based on a genetic algorithm (GA) is provided to solve the problem. The problem formulation and solution algorithm are tested using a numerical example. The GA algorithm was shown to efficiently converge to an optimal or near-optimal solution for the cycle network design. The proposed optimization framework may be adopted by transport authorities and/or urban planners as a decision support tool to help them to systematically identify the best design for a cycle network which balances the benefits and risks to all stakeholders. [ABSTRACT FROM AUTHOR]

Cycling as a mode of transport avoids the negative external costs of driving such as air pollution, carbon dioxide emissions and noise and can also reduce the public health costs associated with physical inactivity. However, increased cycling may also have disadvantages such as increased exposure to air pollution and risk of traffic collisions. A number of studies have developed methods to quantify these health and environmental impacts and have shown that the overall impact of increased cycling is positive. However, while minimising travel costs is traditionally the main objective of transport planners, these studies have not included travel cost impacts in their analyses. In this study, the impacts of a modal shift towards cycling are quantified, taking into account health, environmental and travel cost impacts. It was found that the health and environmental impacts of increased cycling in Dublin, Ireland, would be strongly positive, mainly due to the health benefits of physical activity. When travel costs are also included in the analysis, the central estimate of net impact remains positive but the uncertainty increases considerably. This underscores the importance of the transport and health sectors working together to maximise the social welfare resulting from transport projects. [ABSTRACT FROM AUTHOR]

In recent years, cycling has been recognised by policy makers and practitioners as a sustainable alternative to motorised travel. However, a lack of perceived safety associated with cycling may have inhibited its growth as a popular mode of transportation in urban environments. A questionnaire-based survey, conducted in Dublin city, found cyclists to perceive cycling in the city as less safe than driving. The survey responses were analysed in an ordered logistic regression framework to identify the determinants of their perceived safety in order to recommend possible policy interventions for improvement of these perceptions. A cyclist safety index is also proposed, which allows the perceptions of cyclists relative to driving to be quantified for consideration in transport network design and adaptation for cyclists. [ABSTRACT FROM AUTHOR]

Cycling as a mode of travel provides an opportunity for many people to increase their levels of regular physical activity and contribute to their mental and physical health. Heart rate is often used as a means of measuring the intensity and energy expenditure of physical activity. However, heart rate is also linked to emotional factors such as anxiety and fear. Perceptions of risk due to external factors such as other road users and infrastructure may arouse such emotions in urban cyclists. The present study set out to investigate whether or not perceptions of risk among urban cyclists may lead to increased heart rates. Cyclists completed a test route in normal traffic conditions in Cork, Ireland and heart rates and self-reported risk ratings were recorded in real time. Evidence was found of a link between perceptions of risk and heart rates. This raises questions regarding the use of heart rate to estimate exercise intensity and energy expenditure during urban cycling. The perceptions of cyclists of their safety in relation to various road elements on familiar routes were also assessed, as well as specific events which they perceive to be high in risk. The results indicate that incidents involving car traffic and busy roads which offer no protection from interaction with car traffic are associated with greatest perceptions of risk. [ABSTRACT FROM AUTHOR]