Steve Karmendy and Crystal Green, both 31, and both of College Street in Waynesboro, Pa., died in the crash. They were declared dead at the scene.
Kay Russell, of Carlisle, who was in another car, died several hours later at Hershey Medical Center.
Police alleged that Coble had the cruise control in his truck set at 65 miles per hour and was unwrapping candy when the cars ahead slowed down to the 50 mph speed limit set for a construction zone.
He said he looked up and saw he was "on top of" a line of traffic, according to police.
The accident occurred two miles from where traffic was shifted to one lane northbound because of an ongoing paving project between Exit 10 near Shippensburg and Exit 11 near Newville, Pa.
State Police spokesman Cpl. Kenneth Hassinger said Coble's tractor-trailer collided with the car Karmendy was driving and in which Green was a passenger. Their car was pushed under the car Russell was driving, which in turn was pushed into a truck hauling a flatbed trailer.
The bodies of Karmendy and Green were so badly burned that medical records were needed for identification to be made, according to the Cumberland County Coroner's Office.
Coy, in a letter to Pennsylvania State Police Commissioner Col. Paul Evanko, asked him to order barracks commanders in Chambersburg, Pa., and Carlisle, Pa., to step up patrols in their areas of I-81.
"Truck traffic and speeding motorists make for a deadly combination, especially in construction areas," Coy said in the letter.
"As a regular commuter on I-81, I can say that I have seen an increase in truck traffic and speeders in the same area as the crash," Coy said.
"This much-needed construction project is being done at night which unfortunately is the time when truck traffic picks up," Coy's letter said.
State police in Chambersburg declined to comment on Coy's letter.
Coy could not be reached Thursday night. He said in a written release accompanying a copy of his letter that "increased police presence on the interstate will send a message to truckers and other motorists to slow down or you're going to pay a hefty fine or worse yet you could wind up killing someone.
"This accident should be a wake-up call to all motorists who drive on I-81," Coy said in the release.
The Associated Press contributed to this story.