I was behind one such car on the way home from work, nothing in front of it, braking all the time, it was so annoying and 20 mph inside the limit. Some drivers should not be on the road. Slow hesitant drivers are just as bad as those going too fast, sometimes you can get caught out by someone when driving too slow if you yourself are not fully focused. Those doing 40 on a motorway spring to mind, wouldn't be so bad if they were towing something!
Come to think of it, whenever I see a Police patrol car on the motorway, doing around 68mph
you always see a plethora of brake lights
people panic when they see them!