Calendar Time to Leave Notification calculated on Foot not by Car

I have my calendar alerts set using the “Time to Leave” alerts but the timing of the notifications are being calculated on foot rather than by car. I cannot see anywhere to change this or why this is happening on my iPhone 12 - it is not doing it on my iPhone 8. Please note this is NOT the add travel time to calendar function - it is the Time to Leave alert.

Does anyone have any suggestions please?