Question: When travelling with others, is it best for everyone to recite tefillas haderech, or can we listen to one person recite it and say amen?
Answer: The Shulchan Aruch (OC 124:1) writes that the chazan repeats the amida (chazaras hashatz) on behalf of those that do not know how to daven. However, the Mishna Berura (124:1) writes that this only applies to one who is not able to easily daven by themselves. One who is able to daven properly cannot fulfil their obligation simply by listening to the chazan’s repetition.
The Gemara (Berachos 29b) refers to tefillas haderech as a tefilla. Therefore, R’ Avraham Dovid Horowitz (Kinyan Torah 2:119:2) writes that one who is able to easily recite tefillas haderech should do so, rather than listen to another recite it on their behalf. However, he justifies why people are generally lax about this, differentiating between the amida that everyone is supposed to recite three times every day, and tefillas haderech that one only says when travelling.
Nonetheless, the Mishna Berura (29:15) writes that while this applies to the amida, it does not apply to most other berachos. The berachos before shema in shacharis and maariv are requests for mercy, and therefore they should also be recited by each individual. However, one may fulfil one’s obligation for other berachos by listening to others and saying amen. Thus, R’ Avraham Dovid Wahrman (Eshel Avraham 2:110:4) writes that one who is travelling can say tefillas haderech on behalf of others (See Piskei Teshuvos 110:3).
In conclusion, it is preferable for everybody to say tefillas haderech by themselves, rather than listen to another saying it.