Measuring Accessibility: A Guide for City Practitioners

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Since 1956, the US has spent $10 trillion on highways—more than twice the cost of transit, intercity rail, aviation, and ports combined. And for that astronomical sum we have 2.9 million deaths; crumbling streets and bridges; growing highway congestion; and the largest contributor of climate pollution. 

This is in large part due to our focus on measures that seem obvious but can lead in the wrong direction. We have long judged the success of our transportation system on the speed of cars – a scale called “level of service” (LOS). When cars are slow and congestion increases, we tend to widen roads to speed them up. 

But we have new evidence to show that focusing on LOS alone misses the mark – generating new traffic by luring more drivers onto the road more often; by making trips by foot, bike or transit difficult or more dangerous; and by fostering development that is more spread out.

As a result, highway widenings tend to provide little relief and impose long-term burdens like higher costs; longer travel distances; and diminished environmental, safety and quality of life outcomes. These burdens have hit low-income workers and communities of color especially hard. Many historically Black communities, for instance, have been displaced, cut off, or directly impacted by crashes and pollution from nearby highway projects. Meanwhile, many low-income workers must maintain and fuel vehicles they cannot afford.

Accessibility is a measure that better captures what we want out of our transportation system than LOS alone by describing how easily travelers can reach destinations, not just how fast we can get from one door to another. If we have a transportation system operating at a high LOS, but destinations that are sparse or distant, we may still have poor accessibility. Conversely, we may also have poor LOS but very dense and close-by destinations, resulting in good accessibility. Of course, the best accessibility case is a well-functioning transportation system and short travel distances.

And when we have good accessibility, we can be more confident about a variety of good policy outcomes that are equitable and sustainable.

In their latest report, Measuring Accessibility, our colleagues at the State Smart Transportation Initiative (SSTI) provide policy makers and practitioners with an easy to follow guide for measuring accessibility. Mayors can support improved transportation systems by sharing this report with their transportation leaders.

SSTI works with state DOTs, metropolitan planning organizations (MPOs), local governments, and experts in the field, building on decades of relevant research, to help set up analytic platforms, integrate the right data sources, create workflows, and establish standards to guide the emerging field of accessibility analysis. Our research also helps tie accessibility to other important outcomes like vehicle miles traveled (VMT), mode choice decisions, and transportation costs.

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