The majority of poskim take on that if one needs to travel on Shabbos for reasons of pikuach nefesh, i.e. a pregnant lady, hatzolah member, police, doctor etc. then he/she is obligated to recite Tefillas HaDerech and there is no problem of asking for personal requests on Shabbos. Seemingly, this would be like the halachah in Shulchan Aruch (288:10): דזועקין ומתחננין בשבת לכל חולה שיש בו סכנה – “We cry out and plead on Shabbos, for anyone who is sick and in great danger”. Similarly, we find in the Magan Avraham (128:70) and Mishnah Berurah (130, s.k. 4) that if Yom Tov falls on Shabbos and one has a bad dream which he would fast for even on Shabbos, then he may recite the special tefillah in Birchas HaKohanim about dreams even though it contains personal requests, since there is a big need.
The Shu”t Betzel HaChochma (5:41) adds: There is additional room for leniency, as such a tefillah can’t be pushed off, and if Tefillas HaDerech isn’t recited now, it will never be recited (as is clear from the Machatzis HaShekel, 623:3). Consequently, since all roads are dangerous, and Chazal enacted a special tefillah for one to recite in order to be saved from danger, if one needs to travel on Shabbos, he is allowed and is even obligated to recite Tefillas HaDerech.
The Betzel HaChochmah points out: It’s clear from the Shulchan Aruch (267:3) that the berachah of השכיבנו recited in Ma’ariv on Friday night doesn’t end with the phrase שומר עמו ישראל – “The Guardian of His people Yisroel.” The Mishnah Berurah (s.k. 7) explains, that on Shabbos we don’t need protection as Shabbos itself protects us. The source for this is the Taz (s.k. 1). If so, perhaps there is no need to recite Tefillas HaDerech when travelling on Shabbos, as Shabbos itself protects us. However, he quickly refutes this argument, as the Taz himself says: “We know that unfortunately we don’t guard Shabbos well enough”, therefore, we still need to daven for protection. Moreover, the Magen Avraham (s.k. 3) writes in the name of the Zohar, that there is a difference between an individual and the public, and individuals still need protection on Shabbos. He concludes: Tefillas HaDerech should be recited, since one is traveling in a place which is dangerous, and the tefillah can’t be made up for at a later date, and especially since we don’t keep Shabbos properly, we don’t have the special protection of Shabbos.
The She’orim MeTzuyanim B’Halachah (68, Kuntros Achron, s.k. 1) and R’ Sroya Davlitzky (Kuntros Tefillas HaDerech, siman 12) both rule that Tefillas HaDerech should be recited on Shabbos. R’ Yitzchok Zilberstein in Toras Yoledes (Perek 23) writes that if the roads are dangerous then it should be said, and if they are not, then it is likely that the tefillah shouldn’t be said on Shabbos.
The Toras Yoledes writes that R’ Chaim Pinchos Scheinberg zt”l allowed saying Tefillas HaDerech on Shabbos since it is מטופס ברכות, i.e. the personal requests in Tefillas HaDerech are part and parcel of the berachah. He also brings that R’ Moshe Sternbuch writes that the prohibition to ask for personal requests on Shabbos, is only in regard to mundane matters, however, if it is something related to Shabbos certainly one may daven for it on Shabbos (see further Shu”t Teshuvos V’Hanagos 7:37, ois 48).
He further brings that R’ Ben Tzion Felman zt”l writes that if one does an act on Shabbos and asks that it be successful, that is not included in the prohibition against asking for personal request on Shabbos, therefore, if one takes medicine on Shabbos he may recite the “Yehi Ratzon” cited in the Mishnah Berurah (230, s.k. 6) beforehand. According to this, perhaps we can compare Tefillas HaDerech for one travelling on Shabbos to these cases, and one would be allowed to say it.
R' Chaim Kanievsky zt”l (Derech Sicha Vol. 1, pg. 277) was in doubt, as perhaps Tefillas HaDerech shouldn’t be recited on Shabbos, like we find in the Mishnah Berurah (551 s.k. 99) that if a pregnant lady eats a new fruit during bein hametzorim she shouldn’t recite shehechayanu since the only reason she is eating the fruit is because of pikuach nefesh. Perhaps in our case as well, since the only reason one is traveling is because of pikuach nefesh, Tefillas HaDerech shouldn’t be said. Or perhaps, there is room to differentiate, as Tefillas HaDerech is not a berachah, rather it is a tefillah to be saved from bad things, therefore, perhaps it should be recited even on Shabbos.
To summarize: if one is travelling on Shabbos for reasons of pikuach nefesh, some say Tefillas HaDerech should be recited (Shu”t Betzel HaChochma, She’orim MeTzuyanim B’Halachah R’ Sroya Davlitzky, R’ Chaim Pinchos Scheinberg, R’ Ben Tzion Felman and R’ Moshe Sternbuch). Some say that if the roads are dangerous, it should be said, and if they aren’t then it’s possible it shouldn’t be said (R’ Zilberstein) and some are in doubt (R’ Chaim Kanievsky).
