COVID-19 and Traffic Counts: Making Good Decisions with Less Data

April 14, 2020

With traffic volumes down as much as 70% due to the COVID-19 pandemic, our go-to data source – field traffic counts – is at least temporarily unavailable. Knowing that much of the previous demand will return when the worst impacts of the pandemic have subsided, it is to the benefit of our communities, our economy and our infrastructure investments to keep advancing projects. In the meantime, how can we make sound investment decisions without field collected data sources? While not every project type can be addressed equally, Alliant staff are working daily on these evolving issues and embracing a range of strategies.

Cast a Wide Net

For transportation study decisions, data is essential and recent data is the gold standard. But what if we can’t get it? Start with other data sources – all of them. In many cases, past turning movement counts exist at study intersections. Mine this data and other historical counts for the same location. Look for other nearby counts that offer similarities, too. Review historical growth rates and agency transportation plans. Many agencies have system detectors logging data, such as automatic traffic recorders, freeway and traffic signal detectors. This data is accessible through software such as DataExtract and MaxView. These other sources provide a wealth of information when we are not able to field collect traffic data in the here and now.

Collaborate

Many consultants and agencies alike have their own cache of data from past projects, including video archives that may or may not have been previously analyzed. Networking with our peers and agency contacts can help identify count data as well as previous study documents and other data sources.

Go Big

Big data – such as that provided by Streetlight, INRIX, ClearGuide and other companies – is an increasingly valuable tool for understanding traffic. In the wake of COVID-19, these data sets are being explored for new possibilities and will continue to help fill in some of the gaps. Coupling big data sources with other known traffic volume sources to assess seasonal and scaling factors, volume directionality and peak hour factors can provide reasonable estimates for many study applications.

Think Thresholds

The data we get from counts is highly detailed and precise. However, in many study applications the data is still just a snapshot of a point in time. As engineers, we are often comparing new counts with historical data and smoothing data due to other factors such as seasonality, land use changes or volumes from adjacent intersections. Many of these strategies are used even when we can collect new data. But often, the decisions we are making – say adding a turn lane or not – do not hinge on just a single threshold. We need to consider: Are there multiple thresholds for this decision? How close were we the last time we collected data? What would the missing data tell us that we don’t already know?

Consider the Cost of Being Wrong

Are we trying to address an urgent safety issue? Are we developing volumes for traffic modeling? Or conducting a planning assessment of capacity needed in 20 years to address congestion? While we want to make the best decision in any case, the potential consequences of over- or under-investing may give us some clarity regarding traffic data needs and strategies.

Look to the Past

The Great Recession in 2008-2009 resulted in significant traffic reductions for several years. While the similarities with the COVID-19 outbreak may end there, it helps to remember we have seen a “new normal” before when it comes to traffic volumes. We were able to navigate significant reductions in traffic volumes then with thoughtful planning and analysis, and we can navigate in the same manner now.

In conclusion – yes, we still want the best and latest traffic data. It is still the gold standard. But in the absence of gold, we can make good decisions with silver or bronze while still practicing sound engineering and keeping projects moving.

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