Quantifying Sustainability – public transit

In the 21st century there is a need and desire to provide sustainable transportation systems in cities to ensure that they remain vibrant centers of high quality of life and economic development. 

While developing sustainability-oriented vision and strategy is becoming more commonplace, clear measurement of the concept of sustainability in planning, development, and operations is often vague or missing. However, a new set of tools that synthesize innovative research and interdisciplinary problem-solving are set to address this challenge. 

Moving towards Sustainability 
The Public Transit Sustainable Mobility Analysis Project Framework (PTSMAP) developed at the University of Calgary with funding by Steer Davies Gleave and the Natural Sciences and Engineering Research Council of Canada, seeks to provide a means for researchers, consultants, and decision-makers to cut through the complexity of sustainable transportation by quantifying sustainability issues into decision-making criteria. 

After conducting a thorough review of analysis techniques and sustainability literature, a decision-making framework was developed and applied to the analysis of 13 heavy and 20 light rail systems from across the U.S. The framework analyzes the relative ability of different transit modes to support sustainable development and transport goals. To do so, each system is analyzed using 14 factors, such as emissions and energy, accessibility, and economic efficiency, that fall into one of four sustainability categories: economic, environmental, social, and system effectiveness. 

Systems are compared by composite indicators for each of the four categories and one composite factor for overall sustainability. The PTSMAP framework revealed that both light and heavy Rail systems can provide high – or low – performance sustainable mobility. Neither mode showed an inherent advantage. The research suggests that providing sustainable mobility transcends the modal or technology debate and requires a different focal point – one focused on clear sustainability goals such as reducing energy use, operating costs and emissions while improving affordability and quality operations. 

Understanding sustainability – trade-offs and progress
Holistic performance evaluation can be achieved by linking performance measures to a consistent definition of sustainable transportation. This definition should encompass the inputs, outputs, and impacts of the development and operation of transit and be applied consistently throughout the analysis of the system. 

Further, the development of sustainability assessment must focus first on understanding how a transportation system performs on the sustainability factors that fall under this definition. Then a scheme that aggregates those measures for comparison should be developed. This requires measuring impacts – positive and negative – and utilizing a framework that allows objective comparison between systems or alternatives. However, not all factors can be clearly measured at all times due to the time and cost of data collection and the complexity of some sustainability factors. These issues can be resolved over time as quantification becomes part of a wider planning or analytical process.

In many ways the term ‘sustainable’ may be misleading as systems – existing or planned – will make progress towards sustainability goals but never be completely sustainable, and this progress is complex to measure. Through the use of quantification tools, like the PTSMAP framework, the complexity of sustainability can be managed and progress can be measured ensuring greater success in the long term. These approaches provide important guidance for decision-makers and professionals alike in developing sustainable transport and vibrant communities.