One of the biggest risks with 18-wheelers is simply that most accidents come from human error. A driver can make any small mistake and injure or kill people. With their size, these trucks are even more dangerous to other drivers than passenger cars.
You're driving down the interstate at night when a semi-truck passes you and another car. As it goes by, you notice the other car flash its headlights at the truck. It's just a quick flash, perhaps two in quick succession. The truck then flashes back with its taillights and changes lanes.
There are a lot of very dangerous professions in the United States, and people often do not know just how risky they are.
A small mistake by a truck driver can put innocent people in the hospital. If the driver does not see that traffic has stopped in the road, for instance, that semitruck can plow through multiple vehicles before it stops. Distractions are dangerous for all drivers but especially for commercial drivers.
One of the main reasons that a semitruck accident is so devastating for another driver is simply that the truck weighs so much more than that car. Many cars and small SUVs only weigh a few thousand pounds. When they get hit by the semi, it has so much more mass to contribute to the crash that it just tears through the smaller vehicle.
Truck drivers need to be able to communicate on the road, but they also need to be safe. To strike a balance, the Federal Motor Carrier Safety Administration (FMCSA) banned most cellphone use, but they did allow drivers to use hands-free devices in most cases.
If a truck driver falls asleep at the wheel, you now have an 80,000-pound vehicle that is completely out of control. That puts everyone at risk in a heartbeat; even just nodding off for a second can be enough to cause a deadly accident. For that matter, even a tired driver can cause a serious crash without completely falling asleep at all.