Driving east on i-20 after sierra blanca checkpoint starting the incline uphill. i was on left lane, had cruise control set at 80 as per speed limit. on my right a semi just a vehicle away, at my rear another semi also on right lane. front truck started right exit turn signal and just when he started to exit at curve, my vehicle slowed down to 52 in about 2 seconds and semi behind me switched to my lane to avoid semi exiting interstate, semi slammed on his brakes while switching to my lane, hit the horn and i could see the smoke from his tires locking up. my vehicle shifted down to second gear and sped up to 80 mph in about 4 seconds. my vehicle detected the semi on the right lane at the curve, me not knowing if my brakes lights came on as soon as my speed dropped. had my vehicle not sped up right away, the semi would have crashed my vehicle at the curve.