In one sentence, describe what the following article is about:

As night slowly begins to fall over a city's streets and highways, there is almost always an hour or two during which some cars will have their headlights on and others will not. As a general rule, if you notice the day becoming darker (even just slightly), it's a smart idea to flip your headlights on. Though you may not need your headlights to see the road during these times, other drivers may have an easier time seeing you with your headlights on (especially if the setting sun is behind you, obscuring the view of oncoming traffic). Additionally, it's important to note that in many jurisdictions, driving without your headlights on in the evening or morning can be against the law. For instance, in California, headlights must be on from one-half hour before sunset to one-half hour after sunrise (and during any other low-visibility conditions). As a general rule, night driving requires slower speeds than daytime driving. Because visibility is much lower at nighttime than during the day (even on well-lit urban roads), it takes longer to see and react to traffic hazards, pedestrians, and other obstacles. Since you can't control the types of hazards you'll encounter on your drive but you can control your driving, your smartest move is simply to drive slower, giving yourself more time to react to any problems you come across. You'll never want to "out-drive" your headlights — that is, to drive so fast that you can't stop within the distance illuminated by your headlights in front of you. A good rule of thumb for night driving is: "The posted speed limit is the highest speed that's legal — not the highest speed that's safe." Don't be afraid to go slower than the posted speed limit if you can't see very far in front of you, especially if you're rounding a corner or going over a hilltop, where your visibility is further obscured. Allow other drivers to pass you as needed. Statistically, there are almost always more drunk and overtired drivers on the road at night than there are during the day. This can have deadly consequences — for instance, in 2011, drunk driving contributed to more than four times as many accidents at night as it did during the  day. Both of these conditions can dramatically lower a driver's reaction speed and lead to reckless behavior, so keep an eye out for erratic drivers on the road and give them a wide berth. Keep in mind that weekend nights (Friday and Saturday) usually have more drunk drivers than ordinary weeknights because many people choose to start their weekend with a drink or two. Holidays can be especially bad. For instance, some analysis has shown that the early hours of January 1st can be the deadliest time of the year for drunk driving accidents. Just as you'll want to keep an eye out for other motorists who may be impaired by fatigue, you'll also want to make sure to keep your own fatigue in check. Being fatigued on the road can have many of the same risks as being drunk, including decreased awareness, slower reaction times, frequent "spacing out," weaving in and out of the lane, and so on. To fight these problems, be sure to stop frequently, giving yourself a chance to exercise, have some food and/or caffeine, and re-focus before getting back on the road. If you're too tired to drive safely — for instance, if you're having trouble keeping your eyes open — pull over or find a rest stop and get some sleep. It's much better to be safe than sorry and the life-threatening risks of falling asleep at the wheel for just a few seconds are much more important than the inconvenience of being late to your destination. Animals crossing the road can be especially dangerous at night. It can be very difficult to see animals ahead of you on poorly-lit roads when driving at high speeds and crashes involving large animals like deer can be deadly or cause major damage (for the driver, animal, and car). Stay vigilant when you're in places where deer or other animals are likely to cross the road (like rural areas). Pay attention to any animal crossing signs posted near the road and lower your speed appropriately. Additionally, be aware that most deer-related accidents occur in the late fall and  early winter (though they can happen year-round).  If you see an animal ahead of you, the smartest move is usually not to swerve. While it may be your first instinct, swerving is actually the leading cause of injuries and fatalities from deer-related accidents. Instead, lower your speed as much as you can by pressing the brakes and allow your car to hit the animal. One useful trick for spotting animals ahead of you is to look for their retinas. While it's usually difficult or impossible to see an animal's body before it comes into the range of your headlights, you can often see the light reflected in its eyes from much farther away. If you see two closely-spaced glowing dots in the darkness up ahead, slow down! "Spacing out" can be a big problem for nighttime drivers. To stay focused, try to keep your eyes moving while you drive. Constantly scan the road ahead of you for potential hazards. Glance to the sides of the road and check your mirrors occasionally to remain aware of your surroundings. Resist the urge to simply focus on the dividing line in the middle of the road — this doesn't give you much important visual information and can "hypnotize" you into a state of reduced awareness. The relatively quiet, calm atmosphere of most night driving and the uniformity of dark or pitch-black surroundings can combine to put night drivers into a dangerous trance-like state. Even if a driver doesn't outright fall asleep, this distracted state, which can cause lower reaction times, forgetfulness, and other dangerous problems, can be very unsafe. Always stay alert and vigilant — your life and the lives of other motorists may depend on it. It may seem obvious, but it definitely bears mentioning that all of the safety precautions you take during the day are especially important at night. Make sure to buckle up, adjust your seat and mirrors, put away your cell phone, and focus on driving while you're behind the wheel. These simple, everyday precautions make driving safer and accidents less likely, day or night.

Summary:
When in doubt, turn your lights on. Slow down. Be wary of drunk and tired drivers. Take frequent breaks to fight fatigue. Watch for animals, especially in rural areas. Keep your eyes moving. Take all normal daytime driving precautions.