But what if traffic is slow? If traffic is travelling at 80km/hr the entire distance, my 15 minutes grows to 19 minutes, making my total trip only 4 minutes longer. And it is very rare for traffic to travel 80 for the entire trip; usually it is only through the normal slow spots. On the other hand, if there's a small traffic jam, it often takes 10 minutes longer just to get to the next exit, and can easily add half an hour to the total trip. My worst experience with traffic jams added an hour to my half hour trip! And that was not one of the ones where the road was closed by an accident or extreme bad weather.
It may seem obvious, but traffic jams occur when the road is full. They get worse when people insist on changing lanes. Each time a car changes lanes, it is taking up the space of two cars. In other words, a car is being added to an already full highway. Naturally, this just makes the traffic jam worse.
The traffic experts talk about "friction" between lanes of traffic. Traffic jams occur when the "friction" gets too bad. Changing lanes causes friction. How? When you change lanes, you cannot go faster than either of the lanes (or you will hit somebody), and neither lane can go faster than you (or you get hit). That means that every time somebody changes lanes, both lanes must slow to the speed of the slower lane. So every time somebody changes lanes in slow traffic, the traffic gets even slower, ultimately leading to a traffic jam. The best thing to do is relax, be patient, and stay in your lane.
If everyone started doing this, traffic jams would start to melt. Most of the traffic jams are formed near merges, and if the people already on the highway were not changing lanes, then at least the fast lane (the one farthest from the merge) would be able to drive through almost unaffected. Since the traffic jam slows everybody down to about 30km/hr, even one lane going at full speed is going to more than double the ability to get cars out of the traffic jam and get things going again. Stay in your lane. You will still get there faster than if you start changing lanes to 'catch the fastest lane'.