Causal Analysis and Prediction of Human Mobility in the U.S. during the COVID-19 Pandemic

TL;DR

This study develops an analytical framework using Granger causality and regularization techniques to identify key factors affecting human mobility in the U.S. during COVID-19 and compares model performances for predicting vehicle miles traveled.

Contribution

It introduces a combined approach of causality analysis and regularized regression models to analyze and predict mobility impacts during the pandemic.

Findings

Key factors influencing mobility include COVID cases, social distancing, and work-from-home rates.

Ridge regression outperforms other models with the lowest prediction error.

LASSO regression performs better than ordinary least squares in this context.

Abstract

Since the increasing outspread of COVID-19 in the U.S., with the highest number of confirmed cases and deaths in the world as of September 2020, most states in the country have enforced travel restrictions resulting in sharp reductions in mobility. However, the overall impact and long-term implications of this crisis to travel and mobility remain uncertain. To this end, this study develops an analytical framework that determines and analyzes the most dominant factors impacting human mobility and travel in the U.S. during this pandemic. In particular, the study uses Granger causality to determine the important predictors influencing daily vehicle miles traveled and utilize linear regularization algorithms, including Ridge and LASSO techniques, to model and predict mobility. State-level time-series data were obtained from various open-access sources for the period starting from March 1, 2020 through June 13, 2020 and the entire data set was divided into two parts for training and testing purposes. The variables selected by Granger causality were used to train the three different reduced order models by ordinary least square regression, Ridge regression, and LASSO regression algorithms. Finally, the prediction accuracy of the developed models was examined on the test data. The results indicate that the factors including the number of new COVID cases, social distancing index, population staying at home, percent of out of county trips, trips to different destinations, socioeconomic status, percent of people working from home, and statewide closure, among others, were the most important factors influencing daily VMT. Also, among all the modeling techniques, Ridge regression provides the most superior performance with the least error, while LASSO regression also performed better than the ordinary least square model.