I have to agree with Suzyshop1. I have had many a time where you HAVE to go while you are driving or traveling. there is no getting around it. All I can say is that if it is planned, that you watch what you eat prior to leaving. Drink plenty of water!!! If you are alone watch what you eat if you are out. Since you do not know what is cooked or what ingredients are in what you are eating, it is a very good chance yoiu could have an accident. Also carry some Imodium in the car. It is something that all people that have IBS must contend with.
But the best advice is to try to fully understand what foods or stress trigger your BM. Once you can prevent your symptoms, the stress of what to eat and not to eat is greatly eased.