Obviously, there is no precept binding the faithful to do the impossible. Romans do not write laws like that. The faithful, for instance, are not required to live in places where Mass is offered on a regular basis. The church can’t always come to you, and obviously you can’t always make it to church. So obviously it is within the purview of the faithful to recognize when something that is otherwise required is impossible.
A priest acting within the prescripts of his bishop has the authority to grant dispensations. It is not rare for bishops to find travel a just cause for missing Mass on Sunday, particularly if the absence is not in any way habitual:
**Can. 1245 **Without prejudice to the right of diocesan bishops mentioned in ⇒ can. 87, for a just cause and according to the prescripts of the diocesan bishop, a pastor can grant in individual cases a dispensation from the obligation of observing a feast day or a day of penance or can grant a commutation of the obligation into other pious works. A superior of a religious institute or society of apostolic life, if they are clerical and of pontifical right, can also do this in regard to his own subjects and others living in the house day and night.
Now, that is not to say that the faithful do not have an obligation to abstain from affairs that hinder worship. We do. It is to say that a bishop may find travel a just cause to miss Mass, when missing Mass cannot be helped, and so he may direct his priests to give dispensations accordingly.
Even where a dispensation is proper, Catholics are strongly encouraged to observe Sunday as he or she can, under the circumstances:
**Can. 1248 §2. **If participation in the eucharistic celebration becomes impossible because of the absence of a sacred minister or for another grave cause, it is strongly recommended that the faithful take part in a liturgy of the word if such a liturgy is celebrated in a parish church or other sacred place according to the prescripts of the diocesan bishop or that they devote themselves to prayer for a suitable time alone, as a family, or, as the occasion permits, in groups of families.
When a member of the faithful is in doubt about what is possible or not or what is a just cause or not…well, that is why we have pastors. We can ask.