Novel methods for the planning and design of greenways for cycling

Abstract

There is a crisis in transport internationally as the continuing proliferation of car-use undermines environment, society and economy. Cycling has gained considerable attention in policy and academia in recent years as one alternative mode of travel, yet conflict with motorised vehicles and resulting concerns for safety are inhibiting development of this mode. Greenways, as routes for non-motorised travel, offer extensive benefits for the environment, quality of life, tourism and transport; yet their planning and design for cycling has not been thoroughly researched. A review of cycling network planning (including discourse on segregation, vehicular cycling, the hierarchy and challenges facing route selection) highlighted the need for new methods for greenways to focus on safety, environmental impact and economic impact as well as integrating the unique design requirements of cyclists. To this end, the thesis comprises four empirical elements, which are subsequently distilled into a framework for the planning and design of greenways.

Firstly, a mental mapping and modelling approach was developed to identify the determinants of perceived cycling risk, considering both infrastructural and individual effects. A survey (n=104) of cyclists in Galway City (Ireland) collected mentally-mapped perceived risk observations (n=484) and these were matched in ArcGIS to road data extracted from a transport infrastructure inventory. Initial comparison between perceived risk hotspots and locations of cycling collisions showed some alignment between the perceived and objective environment. A Generalised Linear Mixed Model in SPSS revealed the infrastructural and individual determinants of perceived cycling risk to be segregation of infrastructure, road width and the volume of motorised traffic as well as gender and cycling experience. The results illustrate the potential for improved cycling experience in areas well-separated from traffic (e.g. greenways) and the added benefits that these environments can present for women and inexperienced cyclists.

Secondly, an international greenway survey was piloted and deployed online to determine end-user design preferences, receiving 1,002 responses from over 20 countries. Coded qualitative responses initially highlighted high-level user priorities for greenway functions and design priorities. Preferred design characteristics (surface, gradient, width, junctions), facilities (resting areas, food & drink) and other preferences (segregation, parking) were quantified and compared with best-practice. To account for variation in design preferences according to mode of travel, a logistic regression model was built for one design characteristic, surface materials, finding that cyclists, commuters and older people prefer asphalt. Building on existing matrices from engineering guidance, these preferences were incorporated into a framework for the route selection and design of greenways, including as elements: accessibility, safety, user experience, design, environment and economy. This framework facilitates the inclusion of quantitative metrics in a broad route selection methodology, which also allows scope for engineering judgement.

Thirdly, life cycle assessment was used to measure greenway embodied carbon and to develop a balance sheet for the environmental impact of greenways. This approach is predicated on the fact that while modal shift to cycling has the potential to reduce carbon emissions, the carbon footprint of constructing new cycling routes, particularly greenways, can negate these savings. Applying life cycle assessment to the Great Western Greenway (GWG; Co. Mayo, Ireland), embodied carbon due to materials, construction machinery, transport of materials and removal of vegetation and peat was calculated to be 67.6 tCO2e/km.Furthermore, the carbon savings of shifting one passenger-kilometre travelled (PKT) from driving a car to cycling were found to average 134 gCO2e. In this case study, a shift of 115 commuters per year (253,000 PKT) is required to ‘balance’ or offset the carbon footprint ofone 10 km asphalt greenway (over 20 year life cycle).

Fourthly, greenway spending data was derived from the international greenway survey and was used to develop some indicators for the economic impact of these routes. Greenways are comparatively expensive cycling routes to deliver (€100,000/km) and a strong emphasis is placed on demonstrating return on investment. Concentrating initially on the GWG, the average user spend per night was calculated to be €51, confirming earlier findings of economic consultants. Expanding the analysis to the international sample, it was found that the average spend for a greenway user is €47 per night, with accommodation and food & drink accounting for the largest proportions. A Travel Cost Model was then built in SPSS to measure the value of greenway recreation to cyclists showing that the consumer surplus retained by greenway users is particularly high: €77 or 83% of the total value. Meanwhile, the study found broad opposition to direct payment for greenway access. The results show the importance of greenways as a recreational and tourism resource.

Finally, the four empirical elements were combined as part of a framework for the planning and design of greenways and this framework was used to analyse the development of the burgeoning 2,000 km Irish National Cycle Network (NCN). The framework was tested against a case study of the Oranmore to Mullingar section of the Galway to Dublin Greenway, which has recently completed the route selection process, yet faces many engineering, economic and land acquisition challenges. Dividing the study area into three sections, route constraints/opportunities, route options and a preferred route were successfully identified and the result is compared with the output from engineering consultants. Overall, the guidance developed in this thesis will be a major asset to local authorities, engineering consultancies and community groups, enabling the design of safe, environmentally-friendly, cost-efficient and well-used greenways.