COVID-19 Risk Score

FAQ

What is the COVID-19 risk score?

The risk score is a calculation performed by Ride Alert using daily reported and forecasted infection cases for each U.S. county. It estimates the projected chance that at least one COVID-19 positive individual will be present at a ride assuming a given group size. The concept and model were designed by Joshua Weitz, PhD and Director of Quantitative Biosciences at Georgia Tech. A real time, interactive dashboard for assessing event risk was subsequently developed.

Why was it implemented?

To give cyclists better visibility of the COVID-19 risk in their local community when deciding to join group rides.

How is this useful?

Like any projection based on a set of data and assumptions, it's only as useful as you personally consider it to be. The risk score is not a panacea but yet another tool to help cyclists understand infection trends in their community.

How is the group size determined?

The score accounts for the currently confirmed ('in') and undecided ('maybe') participants for a particular ride. This is most likely not representative of the number of people that show up.

Isn't the infection rate much higher than current testing would indicate?

The model uses a factor called ascertainment bias to account for this. The current value is set at 5 (i.e. there are 5 times more active infections than reported by the county agencies).

Why does the forecast for a ride show an upward (downward) infection case trend? That doesn't seem right based on historical data.

The forecasts are generated by the Google Cloud AI and Harvard Global Health Institute project. These datasets are the result of Machine Learning (ML) models that take many factors into consideration. The full white paper describing their approach is available here.

Why does the COVID-19 risk show No Data?

A calculation requires a 14 day window of cumulative reported and forecasted cases. If the ride start date is far enough in the future, a forecast is not yet available. Additionally, a small set of state heath agencies do not report at the county level.