see signals? vRooooommmmmmm!!!!!

A car driving at about 40km/h, keeping a distance with the car in front. Then suddenly, he saw this car at another lane, signaling trying to get into his lane. Immediately the car from 40km/h changed to 110km/h.

Does this sounds familiar? I've seen this on the road almost EVERYDAY!! If the car was on his full speed and he doesn't want to step on the brakes, still understandable, but all the while he's driving slow, then when he saw the signal, he doesn't feel comfortable and he doesn't want ppl to overtake him! so strange la these ppl.. maybe all the while he's following a red car, so he doesn't want to change to follow a black car? what you think? hehe... no wonder a lot of cars choose not to put on signal when they decided to switch lane..