Its hard to get far on the road before you encounter a semi-truck. While you might think they are "just another vehicle on the road" or a "50,000 pound hunk of metal," that can sometimes be far from the case. Keep in mind that truckers are really "at work" when they are on the road -- most are some transporting thousands of dollars worth of merchandise and on a time restriction. Thus, it is a good idea to become familiar with signals that truck drivers may send to others on the road.
Truckers usually communicate with each other using citizen’s band (CB)
radios, but they communicate with you using headlights, turn signals and
trailer lights. In many cases, you probably don’t realize they’re
doing it.
According to Chad Upton of brokensecrets.com, "Trucks have a lot of advantages over the average driver. For example,
they sit a lot higher, so they see past other cars when you can’t. Also,
from their CB radio, they know about things that are around the next
corner."
A common trucker courtesy is to alert oncoming traffic of an upcoming speed trap. Through CB radio, drivers are often alerted ahead of trap, allowing them to adjust their own speed and notify others do the same by flashing their lights -- however, this is illegal in some places, so check your local laws! Due to a semi's extreme size and weight, it can be slower than the average vehicle to make a lane change. A common "lay-driver" courtesy is to flash a truck driver if he/she is allowing a merge.
Upton also says, "Truck drivers will put their flashing hazard lights on when the highway
traffic is coming to an abrupt stop. This signal is fairly common
among drivers in Europe, but is only common among truck drivers in
North America. If you understand this signal, you’ll notice it from a
great distance and you won’t have to jam your brakes at the last minute."
Lastly, you can invest in a CB radio yourself to become more with trucking lingo while on the road!