By Tatiana Peralta-Quirós
without a car in, say, 30–75 minutes—a practical criterion for judging the state of mobility and for designing ways to improve it. Using the accessibility criterion will be critical to achieving SDG 11, the United Nations’ Sustainable Development Goal to “make cities and human settlements inclusive, safe, resilient and sustainable.”
The ability of residents and businesses to access markets,
employment opportunities, and service centers such as schools and hospitals is
critical to urban economic development. Recognizing the importance of mobility,
the UN has included transport in SDG 11 as Target 11.2, which reads, in part,
“By 2030, provide access to … sustainable transport systems for all, improving
road safety, notably by expanding public transport, with special attention to
the needs of those in vulnerable situations….”
Quantifying the Goal
The SDGs tackle the question of how to measure the targets
by providing draft indicators. The two indicators for Target 11.2 cover cities
with a population greater than 500,000: “Percentage of people living within 0.5
km of public transit” (Indicator 11.2.1) and “Km of high capacity (BRT, light
rail, metro) public transport per person” (Indicator 11.2.2).
However, these indicators miss the essential goal of
transport and mobility, and planners should move away from these and other
proximity-based indicators in assessing urban mobility, for at least three
• For households and firms, the transport system itself is not important. Rather, its key attribute is the access it provides to resources and employment opportunities.
• Defined in this way, accessibility can be a powerful design tool that allows planners to gauge the effects of changes in transport and land-use systems.
• For policymakers, citizens, and businesses, the accessibility of jobs, services, and markets offers the clearest way to discuss
the state of the transport system.
A Better Measure
An “accessibility analysis”—building on the work of urban
economist Alain Bertaud— calculates the number of jobs, educational centers,
health centers, or other resources that are reachable within a certain travel
time, either from a selected place or on average by all residents.
Accessibility analysis has not always been feasible. Today,
however, with the growing availability of standardized data and better
computing resources, a transport project’s benefits to the residents of, say, a
low-income neighborhood can be assessed with a metric more meaningful than a
projection of reduced congestion or transit ridership.
For example, road congestion may be a constraint in a
dispersed urban setting with inadequate transit, walking, and cycling options.
But an accessibility analysis can show that improving multimodal options may
yield far greater mobility benefits than a focus on infrastructure or travel
From Research to Practice
The transition of the accessibility indicator from research
into practice is yielding a better understanding of their value in promoting
sustainable urban mobility. For instance, Bertaud has constructed a measure
that defines the effective size of the labor market in a metropolitan area by
calculating the share of the area’s jobs accessible within 60 minutes. Applying
the measure to greater Buenos Aires indicates that, on average, a resident
there can access approximately 34 percent of the jobs in the metropolitan area
in 60 minutes (recognizing that actual accessibility varies by specific
The accessibility type of indicator provides a clear and
relevant way to compare transportation scenarios in one city or compare cities
across regions. And it provides a fruitful basis on which to publicly
communicate the value of different transportation interventions.
Indeed, the accessibility-based indicator has already been
applied in numerous other cities to calculate citywide accessibility of
employment opportunities, schools, hospitals, retail centers, and so on. The
calculations have revealed areas that, for example, are densely populated yet
have poor accessibility to one or many types of service. Similarly, the
analysis can identify areas that have good accessibility but have a low
population density and thus have the potential for greater development.
An open-source software platform for measuring accessibility,
the Open Trip Planner Analyst (OTPA) accessibility tool, is available to
government officials and all urban transport practitioners. Developed by the
World Bank in conjunction with Conveyal (http://conveyal.com),
this tool leverages the power of the OTPA engine and open standardized data to
model block-level accessibility. The added value of the tool (free and user
friendly) is its ability to easily calculate the accessibility of various
opportunities and transportation scenarios.
To evaluate the true benefits of urban transport investments
and policies, the SDG indicator for Target 11.2 should measure accessibility.
That type of indicator offers the most comprehensive measure of transport
impacts on access to employment and commercial opportunities, health,
education, and other essential services of urban life.
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