The Shulhan Aruch (Orah Haim 249) writes that one who is planning to travel on Ereb Shabbat, must make sure to give himself enough time to arrive at his destination before the arrival of the Shabbat. Hacham Bension Abba Shaul (Israel 1923-1998) in his Or Le’sion (15:6) suggests, that one who is traveling on Ereb Shabbat should at least give himself a window of time of an hour when he should arrive at his destination. This will solve the problem of traveling on the Shabbat, for even if there was to be unexpected traffic or an accident on the road which will delay him, he will still have an extra hour to work with. This of course is only on a regular week, however, if one is traveling on a Friday which is prone to having traffic, he must take this into consideration, and make his own calculations.
Hacham Bension Abba Shaul (Israel 1923-1998) writes, that this is all talking about where a person is driving himself, or he is having a non-Jew drive him. However, if a person is having a Jew drive him , it is not enough do make sure that he is getting home in time for the Shabbat, rather he must make sure that his driver also has enough time to get home before the arrival of the Shabbat. This Halacha even applies when a person is using a non-observant Jew who anyways would have desecrated the Shabbat if he wasn’t driving him, however since in this case, he was the cause of him driving on the Shabbat, he will be responsible.
