Traveling On Erev Shabbos:
One must reach his Shabbos destination prior to 4 hours and 48 minutes [see footnote] having passed from the beginning of day. [See Q&A] This is due to concern that if he arrives later than the above time there will not be enough time to prepare food for him for Shabbos. This applies even if one is traveling for Shabbos to his own family, as we suspect that perhaps they do not at all know that he is arriving and will thus not have prepared food for him. (This applies whether one is traveling by foot, horse, caravan, [bus, car or train] and thus one must arrive to his destination prior to 4 hours and 48 minutes into the day lest he not have enough time to prepare food for Shabbos.)
In the following cases the above obligation does not apply and one may travel to his destination anytime on Erev Shabbos:
- One has already informed his host, or family, that he will be coming for Shabbos. [One must inform the host prior to 4 hours and 48 minutes passing from the start of the day.]
- The host has a custom to cook a lot for Shabbos in way there is anyways always enough food for guests to eat even without prior notice. Thus being that today majority of people cook extra food for Shabbos, if one plans to eat by a host or by his own family at that destination, it is no longer the custom to be careful to arrive at his destination prior to the above mentioned time.[Likewise if it is common to sell readymade Shabbos foods at one’s destination, he does not need to be careful to arrive prior to the above mentioned time.]
- If in the area one is now in he is unable to prepare for himself Shabbos food, and is unable to eat as a guest in another’s home in that area, then he may travel to the nearest area which has food for Shabbos even if he will only arrive at the end of the day.
- If the area one is now in is a place of danger then he may travel to the nearest safe area even if he will only arrive at end of the day, as to remain in an unsafe area will make him completely devoid of Oneg Shabbos.
In today’s times that families generally prepare extra Shabbos food it is permitted to travel to the home of one’s host any time on Erev Shabbos, even if the host has not yet been informed of one’s intended arrival.  It is certainly permitted to travel any time on Erev Shabbos if one has already informed his host of his intended arrival.
Practical application of when the above travel limitation would apply: The application of the above law in light of today’s advanced form of communication would be practical mainly in a scenario that one is traveling to a hotel or cabin for Shabbos and will be making his own food upon arrival, in which case he must arrive prior to the above mentioned time. [See Q&A]
What is defined as the beginning of the morning from which one begins counting the 4 hours and 48 minutes?
The Ketzos Hashulchan questions whether the day begins from sunrise or dawn. Although he leaves this matter without a conclusion, nevertheless he does conclude that according to the Peri Megadim the calculation is started from dawn.
If one does not have a prearranged meal [or a host to eat by] at his destination and it is already past the beginning of morning, how much time does he have to travel?
He may only travel until 4 hours and 48 minutes from morning. If this time has already arrived he may no longer travel at all, and rather is to prepare for Shabbos in his current area.
How close to Shabbos may one travel in a case that he has already informed the host of his arrival?
It is best not to arrive too close to Shabbos as this can lead to Chillul Shabbos. This especially applies when traveling by car, as cars easily break down and may take many hours to fix. It is thus proper not to travel a long distance from home very close to Shabbos.
May one travel on a plane which will be arriving close to Shabbos?
See above Q&A. The Ketzos Hashulchan suggests even regarding cars [of his time] that one should not travel a great distance at all on Erev Shabbos, and certainly not past midday. This obviously would apply tenfold with regards to flying, of which delays are very probable and common.
If one already cooked all his meals, must he still reach his destination prior 5 hours into the day?
If one has readymade food with him, and thus does not need to prepare food for Shabbos upon arriving in his destination, then logically speaking he may travel throughout the day, and so rule most Poskim. However some Poskim rule that even in such a case he must arrive at his destination prior to the above mentioned time.
Regarding the opinion of Admur, see above mentioned footnotes.
If one is traveling with raw foods which still require preparation, then according to all the traveling restrictions apply and he must arrive to his destination within 4 hours and 48 minutes from the beginning of the morning.
If one is traveling to a hotel for Shabbos and will be eating his own food, must he arrive at his hotel within 4 hours and 48 minutes from the morning?
Depends; If the traveler is taking readymade Shabbos foods with him, then there is no need to arrive within the above mentioned time. However if he will need to prepare the food upon arrival then all the traveling restrictions apply and he must arrive within 4 hours and 48 minutes into the day.
May one travel close to Shabbos on a bus or taxi driven by a Jew, if doing so may cause him to travel back to his destination on Shabbos?
Many Gedolei Yisrael have advised to only travel on Erev Shabbos with enough time for the driver to return back to his destination before Shabbos.
 249/3; Lit. “One may not walk more than 3 Parsaos”. The intent of this is to say that one may not arrive past the amount of time it takes to walk this amount of distance. Practically in time amounts, the amount of time it takes to walk 3 Parsaos [12 Mil; 4 Mil per Parsa] is 4 hours and 48 minutes according to ruling of Admur in 459 that a Mil is 24 minutes, and so rules Magen Avraham. However according to those opinions [Michaber and others] which rule that a Mil is 18 minutes the amount of time it takes to walk 3 Parsaos is 3 hours and 36 minutes. According to them one must arrive at his destination within 3 hours and 36 minutes from the beginning of the morning.
 So adds Admur [and Mishneh Berurah 249/1] “from the beginning of the day” as is the wording in the Rambam. However the Michaber simply writes not to walk 3 Parsaos” and omits “from the beginning of the day. This can allow one to learn that the Issur is specifically to travel a distance of 3 Parsaos by foot, as by foot one can become tired and will no longer be able to travel. However by caravan or horse it would be allowed to travel any time during the day, and any distance of travel, as learns the Bach. Thus Admur’s addition of “from the beginning of the day” negates this explanation. [see Peri Megadim 249 A”A 1 and coming footnotes]
However Tzaruch Iyun why the wording in the Shulchan Aruch is not written as brought above “one may not arrive at his destination past etc” and rather they write simply that it is forbidden to walk more than 3 Parsaos from the beginning of the day. This latter wording [besides for not being a clear definition of the prohibition] can lead one to wrongly deduce that the entire Issur is for one to walk more than 3 parsaos, similar to the way the Bach learns, and not that he must arrive by a certain time. Vetzrauch Iyun. Perhaps however one can say that the Sages wanted to teach us that by walking, he may never walk more than 3 parsaos from daybreak, irrelevant to how long or short it takes him [as rules Admur in 249/3], and thus they did not word the prohibition “one must arrive by this and this time”. In any event it remains clear from the Halachas brought in Admur [1-4] that the prohibition applies in all cases, whether by walking, traveling by car or the like, and that its intent is that when traveling by car and the like one may not arrive past the above mentioned time, and not that there is a limit in how much of a distance one may travel.
 Lit. Bnei Beiso. So writes Tur/Michaber/Admur.
 249/3 Parentheses are in original. When traveling by foot one may not walk more than 3 Parsaos from the beginning of the day [even if he is able to walk more than 3 Parsaos within the above mentioned time]. However when traveling by horse, car and the like then he may travel even many Parsaos, so long as he arrives within 4 hours and 48 minutes from the beginning of the day. [249/3]
Other Poskim: However there are Poskim [Bach, brought in M”A/M”B 249/1; similarly Admur only brings the previous ruling in parentheses thus hinting to the possibility of learning as does the Bach] that rule that when traveling by horse and the like one may travel anytime on Erev Shabbos, even past midday, as they learn that only when traveling by foot does the above suspicion apply, as he may become tired out. [Peri Megadim 249 A”A 1 as he learns Bach]
 Pashut, as otherwise it is similar to arriving pass this time.
 249/4. The wording of Admur seems to imply the following:
- One may travel anytime on Erev Shabbos even if he does not know for a fact that his potential host in truth makes extra food for Shabbos, being that majority do so.
- If one does know for certain that a certain host does not make extra food for Shabbos, he must arrive prior to the above mentioned time, unless the host has been made known of his arrival. [However perhaps one can say that even in such a case one may arrive later as even if his potential host will not have enough food, there are others who will].
- If one will be making his own food upon arriving to his destination, he must arrive prior to the above mentioned time.
To note: The Ketzos Hashulchan 69/2 rules plainly based on the above Halacha that whenever one is traveling to his family or a host he may travel any time during the day.
 Kaf Hachaim 249/8
 So summarizes Ketzos Hashulchan 69/2 as the final ruling from Admur, and so rules Piskeiy Teshuvos 249/1
 In all cases when one informs the host of his arrival prior to 4 hours and 48 minutes into the day then it is not necessary for one to arrive at his destination prior to 4 hours and 48 minutes into the day. Rather he may arrive any time before Shabbos. If however the above conditions do not apply one would have to arrive to his destination within the above mentioned time.
 This follows the ruling of Admur that rules even when traveling by car one is to arrive within 4 hours and 48 minutes. However according to the Bach when traveling by car no restrictions apply. Vetzaruch Iyun on Piskeiy Teshuvos 249/1 which plainly rules like the Bach and does not take into account the ruling of Admur.
 Ketzos Hashulchan 69 footnote 1
 There is a dispute between Rash/Tosafus as to when one is supposed to begin traveling by day. The Torah states that one is to begin traveling only by the time of which it says “Ki Tov” Rashi learns this to be from sunrise while Tosafos learns this to be from dawn. Hence, in our case this dispute would likewise apply. However there is room to say that regarding this matter, the sages began their calculation from dawn, even according to Rashi. [Ketzos Hashulchan ibid]
 Vetzaruch Iyun as to his exact reason for learning this way in the Peri Megadim.
 Peri Megadim, brought in Ketzos Hashulchan 69 footnote 3, as is the simple understanding of Admur.
 Ketzos Hashulchan 69 footnote 5; Mishneh Berurah 249/3
 Such as carrying, Muktzah, walking past the Techum Shabbos, Amira Lenachri.
 69 footnote 5
 Ketzos Hashulchan 69 footnote 5
 Perisha; Eliya Raba brought in Biur Halacha Veyuchal and Shaar Hatziyon 249/9; and so seems to rule Peri Megadim 249 A”A 2; so rules Ketzos Hashulchan 69 footnote 4 in his final conclusion of how to learn Admur.
 Olas Shabbos [brought in Mishneh Berurah; Ketzos Hashulchan ibid] as is the simple reading of the Beis Yosef; Levush and Admur in the words “If one has Shabbos food then if it is a place of danger he may travel to another place”, thus implying that even when one has ready Shabbos food the traveling restrictions apply. However the Ketzos Hashulchan [ibid] learns that Admur is simply referring to raw foods which still require cooking and preparations and in such a case the traveling decree applies, as one may not arrive with enough time to prepare them. Thus states Admur that in a case of danger even when one has to still cook his food he may travel. However when one’s food is already prepared then there is no room to make a traveling decree. See Elyah Raba for an alternative explanation of this wording and the Ketzos Hashulchan’s argument against entering this explanation into Admur.
 As Chazal made a “Lo Pelug” in their decree of traveling. Meaning that the Sages did not differentiate between travelers on Erev Shabbos and decreed that all must arrive to their destination prior to the given time.
 As mentioned in the previous question, in accordance to majority of Poskim.