Headlights
Many of the newer automobiles are equipped with fairly bright driving lights. It appears that some driver believe these are headlights, and they will use them when driving in dusk and dawn as well as at night. They do not light up the road very well, but worse than that, they do not activate the tail lights. This makes is difficult to see the car when it is in front of you. This behavior is illegal.

Turn Signals
Use of turn signals is not a suggestion, it is the law. National law requires all automotive vehicles have operational turn signal devices installed and that drivers use those signals to indicate any lane change or turn(1). Turn signals are standard on every automobile manufactured since 1956. Using turn signals allows other drivers to know the intent of a driver to change lanes.

Emergency Flashers
It is all too common to see someone driving on the highway with their emergency flashers on. This is illegal in many states(2) and a danger to other drivers in all states. When someone is driver with their emergency flashers, other drives do not have a way of know if someone is going to change lanes (see Turn Signals above). This is most often seen in rainy conditions, which makes the problem worse. Everyone driving knows it is raining, seeing someone with emergency flashers does not tell them something they don’t already know.

Peddling with Both Feet
It has become more common to see drivers of a vehicle equipped with an automatic transmission to use their left foot for the brake. While this in itself is nothing more than a bad habit, oftentimes the driver applies too much pressure to the brake pedal when driving down the highway, this is called riding the brake. Besides potentially prematurely wearing the brakes out and reducing gas mileage due to the break resistance, the real issue for other drivers is that since their brake lights are always on, or are constantly flickering, it is difficult to impossible to determine when the driver is actually intending to stop. Most people that have operated a vehicle equipped with a manual transmission have never developed the habit of riding the brake with their left foot.

Large Trucks in the Left Lane
Most large trucks are unable to keep up with the ambient traffic speed, yet they will drive in the left lane. This crated a dangerous situation because it not only frustrates automobile driver, it is difficult to impossible to see what is in front of the trucks.

References:
1 ~ 5 Traffic Laws You Might Not Realize You Broke
https://trafficschoolonline.com/blog/unusual-traffic-laws
2 ~ Using hazard lights in rain is illegal in some states; use could cost you
https://www.ajc.com/news/national/using-hazard-lights-rain-illegal-some-states-use-could-cost-you/4GKuiHXYiiowRgq5CgPjLP
3 ~ Slower Traffic Keep Right
https://www.mwl-law.com/wp-content/uploads/2018/05/SLOWER-TRAFFIC-KEEP-RIGHT.pdf