Q. 1. When I drive out of Toronto, to the north, west or east, at what points specifically do I need to say tefillas haderech?
2. Would those locations be the same boundaries for techum shabbos?
A. Shulcha Aruch (O.H. 110: 7, from Brochos 29b)) rules that one does not recite tefilas haderech on traveling less than a parsa (approximately four kilometres) after leaving the city. Rosh (Brochos 4: 18) mentions that the reason for this tefila is the danger present when traveling, usually less than that distance there is no sakana.
As a general rule we keep the obligation of reciting brochos limited to the original conditions when our sages established the blessings (see question 708 in this forum in regards to the brocho on Northern Lights.) Travel today is distinctly different from the days when tefilas haderech was established. It is faster and presents different types of dangers than the ones our forefathers faced. Thus giving rise to different opinions in the Poskim regarding when to recite this tefila.
Poskim disagree whether the above distance is measured in time or factual physical space. Meaning the amount of time it would normally take to walk a parsa (about 72 minutes) when travelling by car or similar. Mishna Berura (110: 30) rules that you make a brocho when travelling just a parsa also by train although the time is much shorter. Other Poskim are in doubt. (Avnei Yoshfo O.H. 15) Mishna Berura also maintains that if the road is dangerous you recite even when it is less than a parsa. Divrei Dovid (8), P'ninei Halocho (p. 220) echo the view, when travelling on dangerous roads in Israel.
Horav Shlomo Miller's Shlit'a opinion is that when you have any doubt if to recite or no tefilas haderech, you should say it without Hashem's name.
The same applies in regards to from which point you measure the parsa. Usually it means from the place there is no more houses or farms that would offer some protection. However it is not directly related to techum Shabbos, since as explained, the reason for the brocho is different.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a