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Oregon State Police - Patrol Division

Safety Tip - Following Too Close
FOLLOWING TOO CLOSE - CAN YOU STOP SAFELY?
 
Recommended Following Distance:
Two (2) Seconds when speeds are under 30 mph
Four (4) Seconds when speeds are greater than 30 mph or in heavy traffic
 
Average Reaction Time:
0.5-2.0 Seconds
 
There's a lot that goes into stopping a car!
 
  1. First you have to recognize that there's a problem up ahead and figure out what to do about it, (Should I brake? Should I steer left? Should I steer right?).  That's Perception Time.

    As decisions become more complex with more variables involved and more options available, perception timeis increased.  Consequently as perception time increases, more ground is covered while you're trying to figure out what to do.  The driver's age, vision, hearing, fatigue and experience also affect Perception time.
     
  2. Next you have to get your foot onto the brake pedal. That's Reaction Time.It only takes a tenth of a second.
     
  3. Then you have to get the car to stop.  That's Stopping Distance.

    No vehicle can "stop on a dime. "  How long it takes to stop depends on road conditions, the speed you are travelling, your perception/reaction time and the braking ability of your vehicle.

    Heavy vehicles, such as large trucks and vehicles towing trailers cannot stop as quickly as passenger cars.  (Think about that before you pull out directly in front of one of these vehicles)
     
The following time/distance chart shows the distance traveled while the driver perceives a hazard and reacts to bring the car to a stop:
 

Miles
per
Hour
Feet
per
Second
Perception Reaction Distance Braking Distance Dry Braking Distance Wet Stopping Distance Dry Stopping Distance Wet 
20294419246368
3044664355109121
4059887697164185
5073110119152229262
5581121144183265304
6088132171218303350
6595143201256344399
70103154233297387451
75110165268341433506
For you technical types, this chart assumes an average PR time of 1.5 seconds and a level asphalt surface producing a drag factor of .7 for dry pavement and .55 for wet pavement.  
 
Distances listed are measured in feet.  
 
Following Distance:
You need space to stop safely.  Follow another vehicle at a reasonable and prudent distance for the speed you are driving and for the traffic and roadway conditions.  As your speed increases, the space you leave between your car and the car ahead should increase.

 
Two-Second Following Rule:
Watch the car ahead as it passes a certain point such as a sign, pole or tree.  Then count "one thousand one, one thousand two."  If you pass the same point before you finish the count, you are following too closely and should drop back.  This is the twosecond following rule.  More distance is necessary at night, in poor road or weather conditions or where visibility is limited.
 
When merging into a lane in front of another vehicle, make sure that you also allow adequate distance between your vehicle and the vehicle behind you. In this way, if something-ahead causes you to brake suddenly, you increase the likelihood that the vehicle(s) behind you can also safely slow or stop behind you.
 
ORS 811.485 Following Too Closely; penalty.
 
  1. A person commits the offense of following too closely if the person does any of the following:
     
    1. Drives a vehicle so as to follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of the vehicles and the traffic upon, and condition of the highway.
       
    2. Drives a truck, commercial bus or motor vehicle drawing another vehicle when traveling upon a roadway outside of a business or residence district or upon a freeway within the corporate limits of a city and follows another truck, commercial bus or motor vehicle drawing another vehicle without, when conditions permit, leaving sufficient space so that an overtaking vehicle may enter and occupy the space without danger.  This paragraph does not prevent a truck, commercial bus or motor vehicle drawing another vehicle from overtaking and passing a vehicle or combination of vehicles.
       
    3. Drives a vehicle when traveling upon a roadway outside of a business or residence district or upon a freeway within the corporate limits of a city in a caravan or motorcade whether or not towing another vehicle without operating the vehicle so as to leave sufficient space between vehicles to enable a vehicle to enter and occupy the space without danger.
       
  2. This section does not apply in the case of a funeral procession.  Except for the funeral lead vehicle, vehicles participating in a funeral procession shall follow the preceding vehicles as closely as is reasonable and safe.
     
  3. The offense described in this section, following to closely, is a Class B violation.