Practice the 3-second rule
The simplest way to keep a safe following distance is to follow the 3-second rule. When the vehicle in front of you passes a fixed object down the road, such as a sign or other landmark, start counting to three. (Make sure you’re counting properly; count one-1,000, two-1,000, three-1,000.) If you pass the same point before you make it to three, you are likely too close to the car in front of you and will need to slow down in order to increase your following distance. 
When to increase your following distance
There will be times when you should increase your distance beyond three seconds. Slow down and keep a further distance away from the next vehicle during the situations listed below: [1, 2]
1. Driving in bad weather conditions
Weather that limits your visibility can make it difficult for you to see potential problems. Slippery roads can also hinder your vehicle from stopping in a timely manner.
2. Driving in heavy traffic
When vehicles start and stop suddenly in heavy traffic, the potential for collisions increases.
3. Entering or exiting a highway
As you merge with faster or slower traffic, leaving more room between yourself and other vehicles can improve your ability to safely enter and exit highways.
4. Driving a large vehicle
Large vehicles and trucks towing a heavy load will require more time to stop due to the added weight.
5. Following a large vehicle
Some large vehicles like trucks and buses can block your vision when you follow too closely. Increase your following distance to see around them.
6. Following motorcycles or bicycles
These vehicles can fall more easily, so it’s best to be safe with a greater following distance.
7. Following a vehicle that makes frequent stops
Increasing your following distance behind vehicles like school buses and delivery trucks affords you more time to use your brakes.
8. Being tailgated
If you’re being tailgated (followed very closely by another vehicle), make sure you have additional space between you and the car in front so you can change lanes or allow the driver following you to pass. Staying to the right, unless you’re passing, on multiple-lane roads lets other drivers pass safely; it’s also the law in many states.
Use defensive driving techniques
Knowing how to maintain a safe following distance is a crucial part of defensive driving. Driving defensively means paying attention to the drivers around you and anticipating potential complications before a dangerous event occurs.
Here are four key defensive driving techniques that will help you stay safe:
1. Remove all distractions
Don’t try to do anything that could distract you from driving, such as using your phone, adjusting the stereo, or eating. Pull over if something other than the road requires your attention. 
2. Read all traffic signs and lights
Road signs provide guidance on how you should be driving in a given area. Following the rules of the road — whether it’s the speed limit or traffic direction — can make all the difference for you and the drivers in your vicinity. 
3. Know your stopping distance
Your stopping distance is the distance it takes to completely stop your vehicle — from the time you perceive a hazard to the distance your car takes to come to a complete stop after hitting the brakes. Having a good idea of your vehicle’s stopping distance and the factors that increase it, such as higher speeds, adverse weather, and poor vehicle condition, can help you understand how to avoid unsafe situations. 
4. Stay alert
With defensive driving, you can help ensure you have the time you need to react and find safety in case you do come across something potentially harmful. For complete peace of mind, Nationwide can help make sure you’re well-protected on the road. Learn more about auto insurance from Nationwide.