COVID-19 has disrupted society and changed how people learn, work and live. The availability of vaccines in the spring of 2021, however, led to a gradual return of many pre-pandemic activities in Massachusetts in the fall of 2021. Leveraging data that were collected using a map-based survey tool in the Greater Boston area in the fall of 2021, this study explores changes in travel behavior due to COVID-19 and investigates the underlying factors contributing to these changes. First, a structural equation modeling technique is developed to capture the interactions between various travel choices, including working from home, travel mode use and change in car ownership. Moreover, attitudinal factors such as risk perceptions and attitudes towards WFH are incorporated into the framework to explain behavior changes. Second, a discrete choice modeling approach is taken to study shifts in commuting mode choices in the fall of 2021. The results show that in the fall of 2021, people became more likely to use their cars to commute, and for those who bought cars during the pandemic, they tended to work on-site more. Our findings can provide planners and policymakers with information upon which to base travel demand management decisions in the post-pandemic era.