I use the three-second rule here in Arizona people tend to slam on there brakes at the last minute not even choosing to use a turn signal. I certainly do not wish for my insurance to go up do to not paying attention and driving to close. When monsoon arrives I give myself the old 4 second rule because the roads are so slick and water tends to rise when the rain is heavy. When we lived in LA (Redondo Beach) drivers tended to respect the road and other drivers a litte more so my lag time was 2 seconds.
Driving is a priviledge. Stick by the rule. It saves life. i tailgate and if i see any of you on the roads i won't forget to wave while i am tailgating you
I use the three-second rule here in Arizona people tend to slam on there brakes at the last minute not even choosing to use a turn signal. I certainly do not wish for my *link snipped* to go up do to not paying attention and driving to close. When monsoon arrives I give myself the old 4 second rule because the roads are so slick and water tends to rise when the rain is heavy. When we lived in LA (Redondo Beach) drivers tended to respect the road and other drivers a litte more so my lag time was 2 seconds.
that just sucks because you get into an accident because of other people's negligent driving and it's you who have to pay for it in the form of higher insurance premiums.
I'd love to live in Redondo Beach, if only to get away from the crazy drivers here!
I think that weather conditions and traffic is most important factors to maintain distance from car. As we know the time is changes from country to country. But I prefer 2 second when weather is good and traffic is very low. 3 second when weather is not good but traffic is low. 4 second when weather is bad and traffic is high.
I cannot believe I did not see this thread before. I will now express my view at this important subject, which is different in many points from the opinions expressed at the opening post.
The following distance is required due to the driver's perception and reaction time. The perception time is the time during which the driver sees the hazard, percives it and the need to react and chooses how to react. The reaction time is the time required to translate this into action, plus the actual time it takes to jerk off of the throttle and hit the brakes (and most driver hesistate needlessly at this point) and the two or three tenths of seconds it takes for the braking system to react.
This by itself adds up to around a full second, or even more, depending on the state of the driver. The level of concentration is so widely effected by lighting, changes of lighting, fatigue and physical tiredness from physical activity, food and drink (not alcohol), thoughts, talking to passengers and other factors. There might even be a situation where the brake lights of the lead car are malfunctioning, further increasing the reaction time, especially in the dark!
Now come the braking abilites of the vehicles, which clearly don't all brake alike, without even mentioning the differences in braking distances between different kinds of cars like sportscars and big rigs. Also, the speed of two cars following one another might not be perfectly identical, slightly gaining up and back from the car ahead.
Likewise, the two cars might not be on the same slope (if you just came down a small downhill slope) or on identical surfaces. Also, small differences in tires, tire wear and age, tire pressure and even the temperatue of the tires, as well as the state of the dampers, brakes, brake fluid, wheel alignment and suspension - can all effect the braking distance.
Another factor is that the driver ahead might collide into another car/obstruction which will halt them at once, or maybe stop and than put the car into reverse, or that traffic behind us might crash into us. Also, objects can fall off of the lead car, or it can spray us with dirt or water from the road, as well as obstruct our view ahead.
Another reason is to help the traffic flow, by allowing for margins that reduce ressistance and allow merging. When following closely behing another car, any little deceleration makes us brake harder, and this leads to a chain reaction that can easily cause a small jam or even a collision further behind.
There are other reasons, and all of them get more and more pronounced with the increase in traffic density and/or the reduction of visibility or road holding. Also, we don't want to be able to stop just short of the vehicle ahead, we need some extra space there, obviously.
This is why a full two second gap is an absolute minimum, suitable for dry conditions where two private automobiles in dry conditions and reasonable speeds, as well as in a normal concentration level of the driver. Three seconds and even four seconds, as well as more than that, should be used depending on the conditions: A car loaded with luggage or even weighty passengers should maintain three seconds, as should heavier vehicles like vans.
When followed closely by another driver, the forward gap should be increased by one second to provide a better cushion that will allow us to brake gently enough for the driver behind to react, too. It also encourages the tailgater to overtake, and allows him to do so safely. If inefficient, the gap should be increased to four seconds.
Cars that get in the way are more of a psychological issue than an actual problem. The amount of drivers the wedge into your gap isn't very large, usualy a few drivers, up to a dozen or so, not more than this. Additionally, almost all of those few drivers that do push into your gap, leave you at least one full second, and quickly turn at a near junction/interchange or move further ahead.
Even if a completly fictional number of sixty drivers were to push their way into your gap, and all remain therein for the whole trip, they would cost us by one minute only! Now that's a small price to pay for preventing the most common kind of car collision. Even a big lost of time isn't worth the risk!
In the wet, the gap should be at least three full seconds, more in you feel necessary (at high speed or particularly slippery conditions), and at least ten seconds in icy conditions. It's important to actually check the distance, at least once or twice each time you drive. Otherwise, you might be closer than you think!
Another problem is with drivers that use a bad method of measurement that look for a moment where the car aheas passes near a light pole. This is too far and can lead to an error of 25% and more! Instead, wait for the lead car to pass over something on the tarmac itself and call "only a fool breaks the two seconds rule" for two full seconds.
Distance at stop lights is also important, for a wide variety of reasons, which I shall discuss in the relevant thread. I recommend at least as much space as to see a foot or two feet of tarmac in between yourself and the car ahead.
Joined: Aug 02, 2006
Posts: 705
Location: McLean, VA, USA
Posted:
Mon Jan 09, 2012 10:54 am
True, you view is different from mine. I think I already did my best in outlining my point and you did not change my mind, so no need to repeat what I said already - readers will have to decide for themselves which approach they like better.
Again, I don't think that we disagree all that much. For instance, I also believe in using a two-seconds gap as a baseline. A three of four second gap should only be used when the circumstances require, but in normal conditions, a two-seconds gap is good enough. So we see eye to eye in here.
I do believe that, if the conditions require it, an increase of the following distance is important, and that in any way it will not cause any inconvenience to anyone, since any lost of time because of it will be insignificant and even if it were to be significant - it's worth it since lack of seperation distance is the number ONE cause of collisions!
The third and last point is that I do believe that following distances should be increased (not too dramatically, I agree) in harder conditions. The very fact that almost any professional and driving-related institute in existance recommends so is good enough a proof, in professional terms, but there is a lot of logic behind it.
While it is true that the stopping distances of both vehicles, front and back, increase and should increase symmetrically, differences in stopping distances between different cars are sharpened as the grip levels drop. Maintainence also carries a big role: A difference of so little as one year of age (regardless of milleage) between two cars, or one car with tires that got a bit more heat during the ride, to make the car behind stop too late.
Also, poor visibility related to road spray and rain contribute to longer reaction times, other factors include heating inside the car, possibly heavy clothing, grime and fumes on the windshield, grime on the lead cars brake lights (as well as the possibility that they are not functioning) and a generally grey background which have a numbing effect on the human mind.
The reduced visibility also means that cars are more likely to brake for hazards ahead and by maintaining larger gaps, you will "buffer" those decelerations and thereby prevent a "shockwave" jam from occuring.
Also, the wet conditions don't just reduce the car's braking distance, they also reduce it's ability to change directions. In some situations, the following distance by itself will not suffice to make a full safe stop, like when the car in front of you crashes and halts at once due to the force of the collision (more probable in wet conditions), when it suddenly shifts into reverse after stopping, or when something falls off of it (again, more likely when wind comes into play)
Furthermore, when the road conditions deteriorate, not only is grip reduced, but it is also rendered much more inconsistent. Dry tarmac surfaces usually hold relativelly constant grip levels, even though some kinds of tarmac is more slippery than others (the smooth, greyish, shiny kind), but in the wet - the grip level changes frequently as the depth of the water film changes, as the abrasiveness and temperature of the tarmac beneath it alternate, and with the presence of slippery agents like oil, dust or even dropped dry leaves on the tarmac. It is very possible for the car in front of you to commence braking while on a less slippery part of pavement than yourself.
In these conditions, you will have to brake and than veer (a skill I described here in the past) and without maintaining enough space this too will be impossible in slippery conditions.
I am not talking theory, these are all scenarios that I have witnessed in collisions that I inspected myself or were told by other professional collision investigators.
You can also look into this discussion, where I brought up the question, and seemed to get the agreement of most of the people involved, most of which being drivers and instructors/observers at the renouned British advanced driving program "Roadcraft."
N.B. The most important point to me, and I believe we can agree on that fully, is that people should actually measure their following distance (in seconds) frequently and accurately, rather than relying solely on their sense. Most drivers I train could follow at a gap of one second or even less, and believe that they are safe with two seconds or more, either because of an inappropriate gauge of distance or an inaccurate method of measurement (like measuring between light poles).
This is also why some instructors teach people to maintain a three seconds gap as a baseline, because due to the inaccurate measurement, those "three seconds" are in fact just two seconds. With the measurement method I suggest this is not needed.
Again, I don't think that we disagree all that much. For instance, I also believe in using a two-seconds gap as a baseline. A three of four second gap should only be used when the circumstances require, but in normal conditions, a two-seconds gap is good enough. So we see eye to eye in here.
I do believe that, if the conditions require it, an increase of the following distance is important, and that in any way it will not cause any inconvenience to anyone, since any lost of time because of it will be insignificant and even if it were to be significant - it's worth it since lack of seperation distance is the number ONE cause of collisions!
The third and last point is that I do believe that following distances should be increased (not too dramatically, I agree) in harder conditions. The very fact that almost any professional and driving-related institute in existance recommends so is good enough a proof, in professional terms, but there is a lot of logic behind it.
While it is true that the stopping distances of both vehicles, front and back, increase and should increase symmetrically, differences in stopping distances between different cars are sharpened as the grip levels drop. Maintainence also carries a big role: A difference of so little as one year of age (regardless of milleage) between two cars, or one car with tires that got a bit more heat during the ride, to make the car behind stop too late.
Also, poor visibility related to road spray and rain contribute to longer reaction times, other factors include heating inside the car, possibly heavy clothing, grime and fumes on the windshield, grime on the lead cars brake lights (as well as the possibility that they are not functioning) and a generally grey background which have a numbing effect on the human mind.
The reduced visibility also means that cars are more likely to brake for hazards ahead and by maintaining larger gaps, you will "buffer" those decelerations and thereby prevent a "shockwave" jam from occuring.
Also, the wet conditions don't just reduce the car's braking distance, they also reduce it's ability to change directions. In some situations, the following distance by itself will not suffice to make a full safe stop, like when the car in front of you crashes and halts at once due to the force of the collision (more probable in wet conditions), when it suddenly shifts into reverse after stopping, or when something falls off of it (again, more likely when wind comes into play)
Furthermore, when the road conditions deteriorate, not only is grip reduced, but it is also rendered much more inconsistent. Dry tarmac surfaces usually hold relativelly constant grip levels, even though some kinds of tarmac is more slippery than others (the smooth, greyish, shiny kind), but in the wet - the grip level changes frequently as the depth of the water film changes, as the abrasiveness and temperature of the tarmac beneath it alternate, and with the presence of slippery agents like oil, dust or even dropped dry leaves on the tarmac. It is very possible for the car in front of you to commence braking while on a less slippery part of pavement than yourself.
In these conditions, you will have to brake and than veer (a skill I described here in the past) and without maintaining enough space this too will be impossible in slippery conditions.
I am not talking theory, these are all scenarios that I have witnessed in collisions that I inspected myself or were told by other professional collision investigators.
You can also look into this discussion, where I brought up the question, and seemed to get the agreement of most of the people involved, most of which being drivers and instructors/observers at the renouned British advanced driving program "Roadcraft."
N.B. The most important point to me, and I believe we can agree on that fully, is that people should actually measure their following distance (in seconds) frequently and accurately, rather than relying solely on their sense. Most drivers I train could follow at a gap of one second or even less, and believe that they are safe with two seconds or more, either because of an inappropriate gauge of distance or an inaccurate method of measurement (like measuring between light poles).
This is also why some instructors teach people to maintain a three seconds gap as a baseline, because due to the inaccurate measurement, those "three seconds" are in fact just two seconds. With the measurement method I suggest this is not needed.
I like your advice. It's very helpful for a new driver like me. My instructor told me to keep a three second gap too.
Instructors that tell their learners to maintain a three-seconds gap, do so because that people either count too quickly and do not measure the gap accurately enough, or because of other reasons. Anyhow, if there are no reasons to increase your gap - a gap of just over two full seconds should suffice.
Increase the gap when the road conditions are poor (three and a-half seconds at leasT), or when you are not as well focused on driving: Eldery drivers, drivers struggling with attention issues (like ADD or ADHD) or very new drivers, should go for a three seconds gap. Also check the gap more frequently to increase your focus.
A car loaded with passengers and cargo should increase the gap by half a second at least. A truck or van should keep three seconds, where a lorry should maintain four, and another second for each teen feet of length or for when it's loaded.
Cheers for this. Ok, I see. I think at the moment I will stick to a 3 second gap as I get very nervous if I am too near a car in front of me. But then, when the car behind me starts coming nearer, I am forced to accelerate. I have so much to learn still!
Since you are still a learner, a three-second gap seems reasonable. Do check yourself: A gap that might appear big enough can be too short.
As for the car behind you: Don't accelerate away from other cars (unless you drive too slowly from the beginning). If you accelerate forward, you only make your forward gap smaller and the car behind tends to get closer into the space you set free. Instead, INCREASE the gap from the car ahead whenever another car sits too close for comfort.
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