Use your turn signals first to indicate your intent to change lanes. Next, visually scan for adjacent traffic and road hazards, and then execute a safe lane change. By signaling your intentions well in advance, you will be in a safer position to communicate with surrounding drivers and will be able to safely execute the desired driving maneuver. A good safety practice is to signal at least four seconds prior to making a turning maneuver.

Did You Know? A recent study reported that there are approximately 630,000 lane-change crashes annually, including both large trucks and passenger vehicles.
While you certainly wouldn't know it from watching the majority of drivers, using a turn signal to indicate a lane change is generally the law.

Emergency Signals (4 Ways)
FMCSA 392.22 – Emergency signals; stopped commercial motor vehicles:
Whenever a commercial motor vehicle is stopped on the traveled portion of a highway or the shoulder of a highway for any cause other than necessary traffic stops, the driver of the stopped commercial motor vehicle must immediately activate the vehicular hazard warning signal flashers and continue flashing them until the driver has placed the warning devices required by CFR 395.22. The flashing signals should be used while the warning devices are being picked up for storage before the commercial motor vehicle is moved. The flashing lights may be used at other times while the commercial motor vehicle is stopped, in addition to, but not in place of, the warning devices required by this section.

Horn

The horn on a commercial motor vehicle is a safety device that can sometimes be the only item preventing an accident by sounding an alarm and communicating your presence to another vehicle. However, we all know of drivers who have abused the use of the horn, potentially causing an accident by startling another motorist. There have been documented instances of road rage that started with the misuse of a horn. The sounding of a horn is one of the few actions a driver can take that makes an intrusion into the driving compartment of another vehicle. Horns on commercial vehicles vary in size, from small electric (city horns) to large, exterior-mounted chrome-trumpeted air horns. Novelty horns are also popular and can play familiar tunes, such as college football fight songs.

So, what does the Federal Motor Carrier Safety Administration (FMCSA) say about a horn?

The answer is found in CFR §393.81:

Every bus, truck, truck-tractor, and every driven motor vehicle in driveaway-towaway operations shall be equipped with a horn and actuating elements, which shall be in such condition as to give an adequate and reliable warning signal.

§393.81 DOT Interpretations

Question 1: Do the FMCSRs specify what type of horn is to be used on a CMV?
Guidance: No.

Question 2: Are there established criteria in the FMCSRs to determine the minimum sound level of horns on CMVs?
Guidance: No.

Can I drive my commercial motor vehicle if the horn is not operational?
Answer: No.
Answer: CFR §392.7

Equipment, Inspection and Use.

No commercial motor vehicle shall be driven unless the driver is satisfied that the following parts and accessories are in good working order, nor shall any driver fail to use or make use of such parts and accessories when and as needed:

• Service brakes, including trailer brake control
• Parking (hand) brake
• Steering mechanism
• Lighting devices and reflectors
• Tires
• Horn
• Windshield wiper or wipers
• Rear-vision mirror or mirrors
• Coupling devices

Headlights

Many companies now have their trucks programmed to keep the low beam headlights on whenever the engine is running. Many states also have laws requiring headlights to be on whenever the windshield wipers are in use. Both of these are good safety practices.

Are your headlights on your truck "fogged" or dirty?
Do you ensure that your headlights, turn signals, and brake lights are clean during your pre- and post-trip inspections?

According to the National Institute for Traffic and Highway Safety, the number one cause of severe nighttime accidents and reduced driving safety is dim, cloudy, or improperly lit

headlights. If a headlight has ineffective or diminished light output, your nighttime driving safety is greatly at risk. A study by the University of Iowa found that a 20-50% reduction in headlight output leads to a 90% increase in the likelihood of an accident. This is a very unnecessary risk, as it is easy to either clean, replace, or fix these headlights.

Dim it!

Is flashing high beams at cars illegal?

Someone told me that flashing your headlights at a vehicle in front of you, particularly if it is going slow in the fast lane, is a citable offense. Is this true?
Yes, in some states, that is true.

The main concern with flashing headlights at an oncoming motorist is that they may be temporarily blinded, which could create blind spots for other motorists while operating their vehicles, thus creating an obviously hazardous situation.