Part 1: Mixing Qualitative Data into Quantitative Analysis
One of The Untokening Principles for Mobility Justice is to “value community voices as essential data.” I have been thinking about how transit agencies can put this into practice.
This is a three-part series that shows my thinking about data over time. The prequel is the post I wrote on data back in 2017 that mostly focused on how messy quantitative data analysis is. In Part One I discuss my experience in a transit agency mixing quantitative and qualitative data for analysis using quantitative research methods. Part Two is my thinking now on the importance of qualitative research methods and what transit agencies need to do to put qualitative data on equal footing with quantitative data. (Note: I have found a distinction between qualitative data and qualitative research methods useful as my thinking has evolved.)
Quantitative transit data often comes from technology systems (e.g. automated passenger counters or fare collection systems) or survey datasets (e.g the US Census or passenger surveys). In both cases collecting quality data requires investment. The benefits of technology systems are datasets that contain almost all events (a population, not a sample) and the ability to automate some analysis. However, transit agencies can’t rely on technology systems alone, because there is so much information, quantitative and qualitative, that these systems can’t measure.
As a generalization, qualitative data is information that is hard to turn into a number. For quantitative transit analysis, it is needed to answer questions about how people experience transit, why they are traveling, trips they didn’t make, and how they make travel decisions. Qualitative data can come from surveys, public comments at meetings, customer calls, focus groups, street teams, and other ways that agencies hear from the public directly.
In the data team at the MBTA we knew we needed both quantitative and qualitative data, usually mixed together iteratively depending on the type of decision. As an oversimplification, we used data to measure performance, find problems, and to identify/evaluate solutions.
Before you measure performance, you have to decide what you value (what is worth measuring) and how you define what is good performance. Values can’t come from technology and should come from the community. At the MBTA the guiding document is the Service Delivery Policy. In our process to revise this policy, we used community feedback in the form of deep-dive advisory group conversations, a survey, and community workshops. Once we agreed on values, knowing what data we had to measure those values, we needed input to try to make the thresholds match people’s experiences.
For example, we valued reliability so wanted to measure that in order to track improvements and be transparent to riders. This brings us to the question of how late is late? Our bus operations team stressed that they need a time window to aim for due to the variability on the streets. From passengers we need to know their experiences like: is early different than late, do they experience late differently for buses that come frequently vs infrequently, and how they plan for variability in their trips. Then we worked with the data teams to figure out how to build measures using the automated vehicle tracking data to report reliability and posted it publicly every day.
Identifying problems can come from both community input and data systems. Some problems can only be identified through hearing from passengers. No automated system measures how different riders experience safety onboard transit or tells transit agencies where people want to travel but can’t because there is no service or can’t afford it. In some cases, automated data is far more efficient in flagging issues and measuring the scope and scale of problems. For example, we used automated systems to calculate passenger crowding across the bus network and where it is located in time and space.
The MBTA used quantitative data to identify a problem of long dwell times when people add cash to the farebox on buses. The agency decided on a solution of moving cash payment off-board at either fare vending machines (FVMs) or retail outlets. (I will admit more qualitative analysis should have been done before the decision was made.) It was critical to understand how this decision would impact the passengers who take the 8% of trips paid in cash onboard. We used quantitative data on where cash is used to target outreach at bus stops. We did focus groups at community locations. Talking to seniors we found that safety was a key consideration between using a bus stop FVM or retail location. This is the type of information we could have never gotten from data systems or survey that didn’t ask the right questions. The team used the feedback to shape the quantitative process for identifying locations.
A key question is at what points in a quantitative analysis process can agencies rely on quantitative data and when is qualitative data imperative. As a generalization, quantitative research methods aggregate data and people’s experiences. We aggregate to geographic units (e.g. census blockgroups) and to demographic groups. We look at the distribution of data and report out the mean or some percentile. Quantitative data analysts need to look at (and share) the disaggregate data by demographics/geography before assuming the aggregated data tells the complete story. And ask themselves, when do we need more data to understand the experience in the tail of the distribution and when is the aggregated experience enough for making a decision.
The question of the bus being late and the use of cash onboard illustrate this difference. Once we set the definition of reliability, service planners use quantitative data to schedule buses. Looking at a distribution of time it takes a bus to run a route, you know there is going to be a long tail (e.g. long trips caused by an incident or traffic). Even though the bus will be late some percent of the time, it is an efficient use of resources to plan for a percentile of the distribution. Talking to the people who experience the late trips would be useful, but likely wouldn’t change that service is planned knowing some trips will be late. (Ideally riders, transit agencies, and cities work together to reduce the causes of late trips!)
However, on the question of cash usage, looking at the payment data you can’t ignore the 8% of trips paid in cash. The experience of that small group of riders is critical. Likely riders paying in cash rely on transit, experience insecurity in their lives, and a decision to remove cash onboard is a matter of access. Without talking to riders, we have no data on why they pay in cash, what alternative methods to add cash would work best for them, and the impact of having to pay off-board.
In my current thinking, at a minimum, decisions that impact the ability of even a small number of people to access transit or feel safe require a higher threshold of analysis. Agencies shouldn’t rely solely on aggregate quantitative data and need qualitative data on the impacts. The role of transit (and government in general) is to serve everyone, including, and often especially, people whose experience fall in the tail of a distribution. (A very quantitative analysis view of the world, I know.)
The lived experience of the community is critical to transit agency decision-making. There are many types of data that can’t come from automated systems. In my experience transit agencies should mix qualitative data into quantitative data analysis, often iteratively as the data inform each other. In practice this means that the teams doing quantitative analysis and community engagement need to be working in tandem with the flexibility to adjust as new data changes the course of the analysis.