A 5 year old should NOT be riding a bik on a road like this.   They don't have the judgement.   I recently watched a 5 year old shoot out of a parking lot, across the street and missed a moving car by about 3 inches.  He proceeded to go directly towards another car, sitting at a stop sign.  He wobbled trying to decide which way to steer.
This is a city kid, under 12, no helmet, total disregard for traffic safety.   His parents don't come outside when he's out side playing.

The difference between the scenario you presented and what happened here is that the 5-year old's mother was riding with her but on another bike. This was a supervised bike ride, while the city kid you described was clearly unsupervised.

such a sad situation. I hope for a miracle.

a friend on facebook had posted tonite she died! I haven't heard it thur my SIL whose was in contact w/ the family, but i believe the person posting was a very good source too. my prayers will b w/ this family and the truck drive

Being a tractor trailer driver for 15 years and understanding that the wind of an 80,000 lbs big rig can suck a full grow man on a mountain bike under the rear tires at 65mph. This story does not tell the whole story. How fast was the truck going? A tractor trailer is a very dangerous vehicle and should slow down and pass with extream care. If I was to see a family riding bikes with kids; the flashers go on and just like a railroad crossing I am coming to a stop. Most professional drivers would shut it down to a crawl passing a mother and kids on bikes. A big rig is intimidating to children up close and the wind factor is not arrow dynamic. More like a wind tunnel.