Access as a performance indicator in a work-from-home world

David Zipper writes Post-Covid, Transit Agencies Must Look Beyond Ridership  for Bloomberg CityLab.


In the article, Zipper talks about using transit access as a performance measure. My graf below:

The idea of transit access isn’t new, but our ability to put a useful number on it is. David Levinson, a professor at the University of Sydney who has written numerous books about transportation access, says that quantitative breakthroughs now allow planners to make far more precise calculations than before. “We’ve got better data now through the General Transit Feed Specification and GPS, as well as from Census Bureau datasets. For each person, the data tells which block they live in and which block they work in. This didn’t exist at that detailed a level until the mid-2000s.”

Obviously I like access, which measures how many valued destinations people can reach in a given amount of time. But in the end, ridership is the raison d’être for transit shops. For all the access in the world, if a bus doesn’t actually serve any actual people, it has failed.

When the ridership is unknown (e.g. for planning a change in service or new construction, where at best we can make an informed guess about a future number of riders, a guess buried in a lot of modeling obscurantism), then access has to date been an excellent performance metric because access is correlated with ridership. The more places people can reach by public transport, the more places they will go.

Ridership fluctuates for many reasons, pandemic among them. Access will be more stable as an indicator. In the absence of other information, I would argue that increases in person-weighted access most per dollar spent will be the most useful for society. When we find that post-pandemic demand for offices (especially CBD offices) falls, jobs that are nominally at a site, but not really (because of 2, 3, 4, or 5-day per week work from home, or work elsewhere, e.g.) will imply more access than they really create. It will be years before the data properly accounts for this. In a perhaps idealised world in which decisions are made based on analysis, the use of access without controlling for this problem will distort our conclusions about where transit services should run. We will favour serving offices where people don’t actually work 5-days a week over sites like schools and hospitals and factories where they do. 

Where is a job, which was a crystal clear number (not really, but we imagined it was) in the days when people worked 9-5 jobs in offices and factories, no longer has the same kind of meaning, and our accessibility metrics will somehow need to account for this. We may need to fractionalize jobs in our access calculations.

The resulting designs for transit systems will have to catch up with these changes in work patterns.