Not a long drive but there are quite a few view points with some stunning scenery. The total time will depend very much in how long you stop to soak up the view. There are also a few short walks from the view points as well so this will add some time if you choose to go down that path.

Or... you can just drive along it slowly. Most of the spots are well marked. The speed limit is fairly low, and most people in Banff are not in a hurry, so taking a slow drive won't aggravate too many. This is a quote from the Banff township site, "This is a scenic route to drive around. You can take Buffalo Street to go to Surprise corner and keep going to the top of the hill. There is a viewpoint on your left where you can see town of Banff. Keep going North, once you get to the junction you can take a left to get back to the town or turn right to go towards the Hoodoos. After the Hoodoos, keep going and you will end up at a “T” junction, take a left to get on Banff Ave which takes you back to town." Thats about it. The hoodoos are really cool, and the view from there is spectacular; it gives a great view of the Bow River and the Banff Springs Hotel from the back.