New paper out: Future accessibility impacts of transport policy scenarios: equity and sensitivity to travel time thresholds

I'm glad to share that the 3rd paper of my thesis is now published. The study (1) illustrates how one can measure the future accessibility impacts of transport project scenarios; (2) discusses how accessibility analyses can be influenced by the little-known issue of the modifiable temporal unit problem (MTUP); and (3) shows that equity assessments of transport policies based on cumulative opportunity metrics depend on the time threshold chosen for accessibility analysis. One thing in particular I like about this paper is that its findings demonstrate that the most common practice adopted by academic studies and transport agencies when evaluating the accessibility impacts of transportation projects can lead to misleading or partial conclusions if this methodological choice is made uncritically.

The paper will remain open access for the next 40 days or so. Downloaded it here [ungated preprint]. The R scripts used to write this paper and my PhD thesis are available in this GitHub repo.

Pereira, R. H. M. (2019). Future accessibility impacts of transport policy scenarios: equity and sensitivity to travel time thresholds for Bus Rapid Transit expansion in Rio de Janeiro. Journal of Transport Geography, 74, 321-332.

Abstract: 

The accessibility impacts of transport projects ex-post implementation are generally evaluated using cumulative opportunity measures based on a single travel time threshold. Fewer studies have explored how accessibility appraisal of transport plans can be used to evaluate policy scenarios and their impacts for different social groups or examined whether the results of project appraisals are sensitive to the time threshold of choice. This paper analyzes how different scenarios of full and partial implementation of the TransBrasil BRT project in Rio de Janeiro (Brazil) will likely impact the number of jobs accessible to the population of different income levels. The analysis is conducted under various travel time thresholds of 30, 60, 90 and 120 min to test whether the results are sensitive to the boundary effect of the modifiable temporal unit problem (MTUP). Compared to a partial operation scenario, the full implementation of TransBrasil that extends this corridor into the city center would lead to higher accessibility gains due to network effects of connecting this BRT to other transport modes. Nonetheless, the size of the accessibility impacts of the proposed BRT as well as its distribution across income classes would significantly change depending on the time threshold chosen for the accessibility analysis. Considering cut-off times of 30 or 60 min, both scenarios of TransBrasil would lead to higher accessibility impacts in general and particularly for low-income groups, moving Rio towards a more equitable transportation system. However, under longer thresholds of 90 and 120 min, an evaluation of this project would find much smaller accessibility gains more evenly distributed by income levels. The paper highlights how time threshold choice in cumulative opportunity measures can have important but overlooked implications for policy evaluation and it calls for further research on the MTUP in future transport and mobility studies.

PolicySpace: agent-based modeling for public policy analysis

I've posted before about the "Humans of Simulated New York", a comprehensive agent-based model (ABM) of city life that is being led by Francis Tseng.

On a similar vein, my colleague from Ipea Bernardo Furtado has been developing the PolicySpace project, an agent-based modelling platform for public policy analysis. According to Furtado:

"PolicySpace is an agent-based model, including families, citizens, residences, businesses, markets, taxes, mobility, and municipalities, that allows “what-if” questions. It is an in silico laboratory, of extremely low relative cost. Yet, it is flexible, adaptable, that anticipates trajectories and, quantitatively, measures horizontal effects across sectors, places and times. The book reviews the literature, explains concepts, and describes the methodology. It details the model, its parameters, and the full process. It validates the proposal and illustrates with applications."

The platform allows for the ex-ante evaluation/simulation of public policy alternatives in a way that takes into account the emergent complexity of the interactions between portions of society and institutions, in space and time. PolicySpace was originally designed for the Brazilian case but it is easily adaptable to other contexts. The code is written in Python, it is open source and the full code is available on Github. The platform is also modular, so it can expanded in a flexible way to gradually incorporate different aspects considered to be relevant for a variety of policy realms. For example, Francis Tseng is further expanding the PolicySpace platform to incorporate public and private urban transportation at fine spatial scale.

Earlier this year, Bernardo published a book where he presents a literature review of ABM and where he introduces, validates and demonstrates applications of PolicySpace. The book PDF is freely available both in English and in Portuguese.

Give Bernardo a shout if you would like to collaborate on the project, use it in your own applications or just give him some feedback.  He is co-organizing a special issue on Complexity Science and Public Policy, so some of you might be interested in that as well.

image credit: Francis Tseng and Bernardo Furtado

Ex-ante evaluation of the accessibility impacts of transport policy scenarios: equity assessment of BRT expansion

About a month ago, I submitted the 4th paper of my PhD research for publication. The preprint of the paper is available at Open Science Framework (OSF), and you can download it here. Please feel free to read and cite share the manuscript. Suggestions and  criticisms  nice comments are always welcome.

Pereira, R. H. (2018). Ex-ante evaluation of the accessibility impacts of transport policy scenarios: equity and sensitivity to travel time thresholds for Bus Rapid Transit expansion in Rio de Janeiro. OSF Preprints http://doi.org/10.17605/OSF.IO/SUT7R

Abstract:

The accessibility impacts of transport projects ex-post implementation are generally evaluated using cumulative opportunity measures based on a single travel time threshold. Fewer studies have explored how ex-ante accessibility appraisal of transport plans can be used to evaluate policy scenarios and their impacts for different social groups or examined whether the results of project appraisals are sensitive to the time threshold of choice. This paper analyzes how different scenarios of full and partial implementation of the TransBrasil BRT project in Rio de Janeiro (Brazil) will likely impact the number of jobs accessible to the population of different income levels under various travel time thresholds of 30, 60, 90 and 120 minutes. Compared to a partial operation scenario, the full implementation of TransBrasil that extends this corridor into the city center would lead to higher accessibility gains due to network effects of connecting this BRT to other transport modes. Nonetheless, the size of the accessibility impacts of the proposed BRT as well as its distribution across income classes would significantly change depending on the time threshold chosen for the accessibility analysis. Considering cut-off times of 30 or 60 minutes, both scenarios of TransBrasil would lead to higher accessibility impacts in general and particularly for low-income groups, moving Rio towards a more equitable transportation system. However, under longer thresholds of 90 and 120 minutes, an evaluation of this project would find much smaller accessibility gains more evenly distributed by income levels. The paper highlights how time threshold choice in cumulative opportunity measures can have important but overlooked implications for policy evaluation.

Some of the core findings of the paper mentioned in the abstract are illustrated in the figure below. The figure brings box plots that show the distribution of gains in job accessibility via public transport by income groups under partial and full operation scenarios of the TransBrasil BRT project in Rio de Janeiro. The results are shown separately given different choices of travel time thresholds in the accessibility analysis.

Academic Impacts on Governments

It has become much easier to assess the academic impact of published papers and authors (Google Citations Page* and T. Reuters). However, the assessment of academic impact on public policy is not that straightforward, although it's a crucial issue for Research Institutes, Think-thanks and Funding Agencies.

A team at LSE leads a project on the subject and they are developing quantitative metrics for measuring the impact of research in the 'public sphere'. It's the Impact of Social Sciences Project.  self-recommending  Some podcasts of their latest events should be available here:

• The Future of Academic Impacts
• From Research to Policy: Academic Impacts on Government

*I encourage you to register at Google Scholar Citations. This is one of the best ways for academics to compute citation metrics and track them over time. You only need a gmail account and Google does the rest for you. Besides, anyone can register!