Tadoussac has a special place in the mind. Though about the same distance from Montreal as Toronto, it always seems remote, the transition point between near Canada and far Canada. It is also at the mouth of the Saguenay, that most majestic of rivers. You can drive from western Quebec to Tadoussac without using the ferry, but you probably wouldn't; the ferry saves 120
My first visit to Tadoussac was in July 1990. To contradict myself, we drove in from the Lac Saint-Jean area via the north side of the Saguenay, avoiding the need for the ferry at that point. We spent a couple of days camping above the town, took the obligatory whale-watching trip and drove down the shore of the Saint Lawrence for an hour just to see what was there. What we didn't do was take any photos of the ferry, though I do have a photo of my oldest son proudly brandishing his front tooth which fell out on that trip—but I won't inflict that on you. But we did use the ferry to start our return trip to Montreal.
We finally returned to Tadoussac 14 years later in August 2004 after a few days camping in the Hautes-Gorges provincial park. This time the sun was shining and digital had replaced film so I have some ferry photos from that trip. Looking back I remember the queue for the ferry was significant giving me plenty of time to take pictures.
Highway 138 is the longest in Quebec, stretching 1389 km continuously from Trout River on the New York border in the south west to Natashquan in the north east, and then after some major breaks to Blanc-Sablon on the Labrador border. So the Tadoussac ferry gets very busy and will continue to get ever busier. Enlarged dock facilities and bigger boats are on the way. A bridge still seems to be to difficult and expensive to justify.
Tadoussac is a small town that makes a good base for local exploring. It's famous for its whale-watching trips and there are boat trips up the Saguenay and into the Saint Lawrence. And about 5 km east of the town are giant sand dunes which you can ski down!