A fatal collision between a school bus and a truck probably was caused by the bus driver’s mistake and made more severe by the truck being overweight and speeding, said the National Transportation Safety Board.

Killed in the February 2012 crash near Chesterfield, N.J., was 11-year-old Isabelle Tezsla, a daughter of Sgt. Anthony Tezsla of the New Jersey State Police. Fifteen other children, including Isabelle’s triplet sisters, were injured.

The crash might have been less severe, or prevented altogether, if the truck had been equipped with an onboard weighing system and if both vehicles were linked by early warning technologies that are now being tested, the board said.

The bus driver stopped at an intersection but failed to see the oncoming truck, which had the right-of-way, as he started to cross.

The truck struck the bus behind its left rear axle, spinning it around and driving it into a pole. Children who were not restrained by seat belts were thrown about the rear of the bus.

In its preliminary analysis, the board said several factors contributed to the bus driver’s error.

He was fatigued from acute sleep loss and chronic sleep debt, and impaired by side effects from prescription medications.

Also, he had not disclosed details about his medical history on his examination form, and his medical examiner did not do a thorough evaluation.

Had he been forthcoming and if the examiner had been thorough, he probably would not have been cleared to drive, the board said.

The truck, operated by Herman’s Trucking, was a 2004 Mack pulling a loaded roll-off dump container. It was overweight, a fault for which the board blamed both the driver and the company.

The board said the driver should have checked the weight and the company should have made sure he took a route that passed a local weigh station.

In addition, the truck’s brakes were defective: its lift axle brake system had not been properly installed, the board said.

The board is recommending that the Federal Motor Carrier Safety Administration ensure that medical examiners are versed in pharmacology.

It also suggested that the National Highway Traffic Safety Administration require onboard weighing systems for trucks rated at 10,000 pounds or more.

And it recommended that once ongoing research on connected vehicle systems is done and standards are developed, the agency require these systems on all new vehicles.

The research, being done by federal, state and private partners, is looking at wireless systems that can give drivers early warning of dangers that lie ahead.

The board also recommended that Herman’s Trucking develop routing procedures to prevent overloading, and that the National Truck Equipment Association tell its members to be sure their lift axle brake installations are done correctly.

NTSB is an independent agency that investigates crashes and makes recommendations to improve safety. It does not write rules, but its recommendations frequently signal the direction the rule-writing agencies will take.