Alexandria native here. The most polite and not rude thing to do, which could be convenient for them and not an inconvenience to you, is to tell them where you’re going, and if they’re along the way, fine. If not, sorry, I gotta go. The vehicle owner may feel guilty but at the end of the month, who is paying the car note? The insurance? The fuel? Maintenance & repairs? Who is spending TIME behind the wheel? If you continuously offer rides you will become the group chauffeur.