Masshole behind the wheel of a truck

Tim understands weather-related highway accidents. And he groks night-time crashes caused by drunks. But until the other day, while trying to get onto 93 South from 128 South, he could never figure out accidents that happened in good conditions in the middle of the day, he reports on Boston Crazy Driving (fortunately, he has good reflexes):

... Then enter a truck with a cracked windshield lettered with the John L. Ciman masonry company from Peabody. The driver of this truck decides he is going to attempt to exit 128 at 93 FROM THE CENTER LANE. And of course, he does it right in front of me. But the whole isn't big enough for us to merge together. I brake. The guy behind me, coming from 93 North and gaining speed, has to jam on his brakes and beeps. I beep, too for good measure. None of this fazes the good mason ...