Question: If one is eating while travelling by car, may one recite Birkat Hamazon while continuing to travel?
Answer: In the previous Halacha we have explained that our Sages have instituted that one must recite Birkat Hamazon while seated in order for one to have optimum concentration while blessing. We have likewise written that one who is walking on one’s way (outdoors) and eats as he is walking may recite Birkat Hamazon while walking, for if we require this individual to be seated in order to recite this blessing, he will not be able to concentrate as a result of his delay.
Regarding our scenario of one travelling by car, it seems that his law should be similar to that of one walking on one’s way, in which case one need not be seated in order to recite Birkat Hamazon.
One Travelling by Car or Ship
If one is merely a passenger in a car or bus and is not actually driving, it is quite clear that one may indeed recite Birkat Hamazon while travelling, for one is not walking and is actually seated. Furthermore, even if we were to consider it as if this individual were walking, we have already determined that one who eats while walking outdoors may recite Birkat Hamazon while walking.
The same applies to one travelling by boat or riding on an animal in that one may recite Birkat Hamazon while travelling on the ship or riding the animal, even if the ship did not yet set sail when one was eating, for sitting on a boat or on an animal is tantamount to sitting in one’s house and he may recite Birkat Hamazon as usual (see Halacha Berura, end of Chapter 183, quoting Piskei Ri’az, Berachot, end of Chapter 7).
One Driving a Car
Nevertheless, if one is driving a vehicle, it seems that it is forbidden for one to recite Birkat Hamazon while driving. Although the aforementioned Piskei Ri’az (ibid.) rules that it is permissible to recite Birkat Hamazon while riding an animal and one need not halt the animal in order to recite Birkat Hamazon, nonetheless, driving a car is certainly different than riding a donkey or other animal, for one who drives a car must concentrate and pay close attention to the road so as not to, G-d-forbid, be involved in an accident and one will certainly not be able concentrate while reciting Birkat Hamazon.
Similarly, Maran Ha’Shulchan Aruch (end of Chapter 183) rules that one may not recite Birkat Hamazon while involved with one’s work. In Chapter 191 (and in Halacha Berura ibid.), it seems that the reason for this is because when one does so, it appears that one is reciting the blessing in a flippant manner and without concentration and this is degrading to the blessing. Driving a car is indeed similar to involvement in one’s work, for one cannot concentrate properly while driving and it appears as if one is reciting Birkat Hamazon flippantly.
Thus, halachically speaking, one may recite Birkat Hamazon while travelling as a passenger on a car or ship. However, the driver of the car may not recite Birkat Hamazon while driving; rather, he must pull over to the side of the road (obviously if this does not pose a hazard) and only then recite the blessing.
We should point out that Hagaon Rabbeinu Chaim Palagi zt”l writes in his Sefer Ruach Chaim that those who rush to get up and leave the table when they reach the “Harachaman” section of Birkat Hamazon are acting incorrectly, for one should remain seated until "Oseh Shalom" similar to how one would not take three steps back at the conclusion of the Amida prayer until “Oseh Shalom”. He writes another reason for this as well. The great Rishon Le’Zion Shlit”a rules likewise in his Yalkut Yosef (Chapter 183) where he adds that when necessary, when one is rushing for whatever reason, one may recite the “Harachaman” section on the way. He adds that he heard this from Maran zt”l as well. It seems that one driving a car may certainly act leniently and recite this section of Birkat Hamazon while driving, especially when there is a need to do so.