# Person in front of you decelerates--best to brake, or best to change lanes? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 10, 2013, 8:55pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794 "2013-01-10T20:55:55Z")\ **Posts on this page:** 20\ **Page:** 6
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [January 11, 2013, 9:16pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/101 "2013-01-11T21:16:35Z")
> [@MeanOldLady](#): > > Have you ever been on any freeway anywhere on the planet where vehicles moving at 60 mph were traveling 6 car lengths apart? Yes, many times. I expect to see it on I-81 tomorrow (though at 70+ mph). There are vehicle clusters that are closer together, but barring rush hours and holiday travel days it’s usually possible to get away from them. ---
**Author:** ![chiroptera](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@chiroptera](https://boards.straightdope.com/u/chiroptera)\ **Post date:** [January 11, 2013, 9:23pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/102 "2013-01-11T21:23:11Z")
> [@SpeedwayRyan](#): > > When I was a kid, I thought about a system that would either vary the intensity of brake lights or a wide brake light that would light only in the center for light braking, and further out toward the sides as brake pressure increased. A flashing (strobe-style) brake light when high levels of braking are detected wouldn’t be a bad idea either. The current system of the indicator being either on or off for something that can vary as much as braking level is not really a great solution. I will say that on dry pavement, you can hit the brakes pretty darn hard without ABS kicking in, so the threshold might be a bit lower than that. If I have the time and presence of mind and I see some sort of stoppage or big obstacle up ahead, I’ll hit my hazards at the same time as braking…thinking that may better alert people behind me that STOPPING. NOW. is a good plan. The problem I see with front brake lights (interesting idea!) or different brake lights depending on the driver’s brake pressure is you’re still at the mercy of clueless, or momentarily inattentive drivers. And too much reliance on technology - ever been behind someone with NO brake or tail lights? Closest I ever came to rear-ending someone was when the driver ahead of me slowed to make a left turn - on a downgrade, which didn’t help - and neither brake lights or turn signals came on. :eek: I came within inches of slamming into him. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [January 11, 2013, 9:26pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/103 "2013-01-11T21:26:41Z")
> [@MeanOldLady](#): > > That advice is, of course, ridiculous. Have you ever been on any freeway anywhere on the planet where vehicles moving at 60 mph were traveling 6 car lengths apart? Silliness. You must never have driven I80 in the middle of Wyoming. 🙂 ---
**Author:** ![chiroptera](https://avatars.discourse-cdn.com/v4/letter/c/df705f/32.png) [@chiroptera](https://boards.straightdope.com/u/chiroptera)\ **Post date:** [January 11, 2013, 9:29pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/104 "2013-01-11T21:29:20Z")
> [@MeanOldLady](#): > > That advice is, of course, ridiculous. Have you ever been on any freeway anywhere on the planet where vehicles moving at 60 mph were traveling 6 car lengths apart? Silliness. Ha no kidding. There’s “how things ought to be” and “how they ought to be but in real life they never are.” I drive I-75 between Genesee and Oakland/Macomb counties in Michigan quite often. Four or five lanes of closely packed traffic going between 60-80+ mph and it’s pretty much impossible to find a “safety cushion” and stay in it for more than 30 seconds during high-volume traffic. ETA: Except in wide open states like Wyoming, Nebraska, Texas, Montana, etc. 😃 ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [January 11, 2013, 9:31pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/105 "2013-01-11T21:31:38Z")
> [@Frylock](#): > > I’ve never understood how it is possible to follow this principle. The moment I slow down enough to put more than a few car lengths between me and the guy in front, someone slips in. So I have to slow down some more. Rinse repeat. > > AFAICT it’s literally impossible to follow this advice without moving dangerously slow. The way I drive home (which would make your wife stark raving bonkers) I am too often behind someone who believes they should leave 6 car lengths in 15 mph traffic. Yes, people do cut in - and then, with only 4 car lengths ahead of them , they hit the brakes. Over and over. And the next lane over is usually crowded, and if I do try to get around I usually wind up behind, since by long experience I pick the lane which is on average fastest. They poke along, and when they do change lanes - it is almost always to one closer to the fast lane. I really do have to get those phasers installed. ---
**Author:** ![Krouget](https://avatars.discourse-cdn.com/v4/letter/k/b38774/32.png) [@Krouget](https://boards.straightdope.com/u/Krouget)\ **Post date:** [January 11, 2013, 9:33pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/106 "2013-01-11T21:33:19Z")
> [@SpeedwayRyan](#): > > When I was a kid, I thought about a system that would either vary the intensity of brake lights or a wide brake light that would light only in the center for light braking, and further out toward the sides as brake pressure increased. A flashing (strobe-style) brake light when high levels of braking are detected wouldn’t be a bad idea either. The current system of the indicator being either on or off for something that can vary as much as braking level is not really a great solution. I will say that on dry pavement, you can hit the brakes pretty darn hard without ABS kicking in, so the threshold might be a bit lower than that. I think the problem with this, though, is that it wouldn’t change much. A “brake intensity light” would mean people would check to see how progressively hard you’re braking, before doing so themselves, and sometimes, people don’t brake \*enough \*(that is, to engage ABS and keep it engaged). It’s better to teach people to use the brakes more consistently and better aligned with their intentions, instead of tapping them constantly, or riding them unnecessarily (IMO, of course;)). Then there is also the technicality that brakes don’t actually stop the car. Jamming them can certainly stop wheel rotation, but after that, it’s entirely the job of the tires. So while the brake lights may be bright red, it doesn’t necessarily mean it would reflect what happening with the rest of the vehicle, including more brake travel for pad wear. ---
**Author:** ![MeanOldLady](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/meanoldlady/32/10737_2.png) [@MeanOldLady](https://boards.straightdope.com/u/MeanOldLady)\ **Post date:** [January 11, 2013, 9:42pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/107 "2013-01-11T21:42:53Z")
> [@Peremensoe](#): > > Yes, many times. I expect to see it on I-81 tomorrow (though at 70+ mph). There are vehicle clusters that are closer together, but barring rush hours and holiday travel days it’s usually possible to get away from them. Heh, okay fine, so on wide open roads cars can easily be more than six car lengths apart, but on a crowded highway, cars never travel anything like 6 car lengths apart. Leave slightly more than one car length, and someone’s going to cut in. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [January 11, 2013, 9:48pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/108 "2013-01-11T21:48:43Z")
> [@Diamonds02](#): > > For every 10 mph you drive, there’s supposed to be one car length between you and the car in front of you. In bigger areas with more traffic, good luck with that. In my area, seems like the local crackerjacks think having more than five feet between cars is improper and they’ll cut right in if there’s even close to enough space. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [January 11, 2013, 9:53pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/109 "2013-01-11T21:53:14Z")
> [@Frylock](#): > > I don’t think there _is_ a way to unambiguously signal things at that intersection. Yes, there is. If you will be exiting via the cardinal direction opposite to the one from which you will enter, your turn signals should remain off. If you will be exiting via a cardinal direction 90 degrees to the left or right of the one from which you will enter, you should activate the corresponding turn signal. If everyone abided by those rules, it would be absolutely clear what each driver intended to do before he even entered the intersection, and there would be far fewer instances of “oh, according to his turn signal he’s turning right/left, so I can enter the intersection before he’s completely OHSHITHE’SCUTTINGACROSSMYPATH”. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [January 11, 2013, 10:27pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/110 "2013-01-11T22:27:29Z")
> [@Frylock](#): > > I don’t think there _is_ a way to unambiguously signal things at that intersection. How on Earth can you claim that? If you’re turning right onto Nixon, you use your _right_ turn signal. If you’re turning left onto Nixon, you use your _left_ turn signal. If you’re going through the intersection, Dhu Varren to Green or vice versa, you don’t use your turn signal. That’s all the options. There’s no ambiguity. It’s just like any other four-way stop. > [@](#): > > I guess you’re saying there are stop signs that say four-way at this spot. But **the failure of this description to fit with the actual configuration of the intersection** only serves to confuse someone unfamiliar with the place, not clarify. You’re simply not “going straight” from west to east, no matter what the signs say. There’s no failure. The signs _tell you_ what the configuration is. They tell you that it’s a four-way intersection. So you should follow the rules as written for four-way intersections, not try to make up your own rules. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [January 11, 2013, 10:36pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/111 "2013-01-11T22:36:58Z")
> [@ZenBeam](#): > > How on Earth can you claim that? If you’re turning right onto Nixon, you use your _right_ turn signal. If you’re turning left onto Nixon, you use your _left_ turn signal. If you’re going through the intersection, Dhu Varren to Green or vice versa, you don’t use your turn signal. That’s all the options. There’s no ambiguity. It’s just like any other four-way stop. > > There’s no failure. The signs _tell you_ what the configuration is. They tell you that it’s a four-way intersection. So you should follow the rules as written for four-way intersections, not try to make up your own rules. I don’t know, maybe I have the scale wrong here. It looks to me like you first turn a full 90 degree right turn, travel for at least a second or two or so, and then do a full 90 degree left turn. Is that not how it is though? Is the swerve much more slight than I thought? ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [January 11, 2013, 10:44pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/112 "2013-01-11T22:44:56Z")
Also it looks like people coming from the south, for example, can’t see people coming from the west before they make the first (southward turn). Why call this a four-way anyway? How is that more efficient than two three-ways? ---
**Author:** ![Diamonds02](https://avatars.discourse-cdn.com/v4/letter/d/b5a626/32.png) [@Diamonds02](https://boards.straightdope.com/u/Diamonds02)\ **Post date:** [January 11, 2013, 10:55pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/113 "2013-01-11T22:55:18Z")
If someone pulls in front of you, just slow down some more to gain more distance… unless you cruise below the minimum speed limit, which is usually 40 mph. Or, speed up to cut them off. Hey, if they are already putting you in a dangerous situation by pulling in front of you, you mind as well have your way by driving aggressively, back. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 11, 2013, 11:38pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/114 "2013-01-11T23:38:58Z")
> [@Frylock](#): > > See my post a few prior to this one–I don’t think it’s possible to have that kind of awareness. Between the last time you checked and the present situation, you may\* have no idea what unpredictable thing might have happened. You have to check immediately before changing lanes, whether you think you know what’s going on in that lane or not. > > \*I mean if you just looked a second ago and there was no car visible anywhere behind you at all, that’s a different story of course. But for example if you just checked a second ago and there was a car two lanes over and a little behind, you now (even just one second later) have no idea at all whether that car might now be in the lane next to you. You need to check. > > And in my view it’s best to simply get into the habit of checking every time. Otherwise you’re expending cognitive energy on something (trying to decide whether you need to check) that could better be used for other things while driving. knowledge of what’s going on around you _is_ better use. In practice, it depends much on the density of traffic - if it’s quiet, you’ll be aware (from frequent mirror checks) the movements of each and every vehicle in your vicinity - and therefore, you’ll already know if it’s safe to change lanes, or if the car you’ve been watching slowly close in the rear view is too close to permit it. If it’s a busy road with lots of cars travelling at significantly different speeds in the various lanes, then you’ll already know that changing lanes in a hurry is unlikely, and you’ll maybe choose to brake instead. Of course, you still need to check the mirror immediately before any manoeuvre too - it’s not either/or. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [January 11, 2013, 11:58pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/115 "2013-01-11T23:58:16Z")
> [@Diamonds02](#): > > If someone pulls in front of you, just slow down some more to gain more distance… unless you cruise below the minimum speed limit, which is usually 40 mph. > > Or, speed up to cut them off. Hey, if they are already putting you in a dangerous situation by pulling in front of you, you mind as well have your way by driving aggressively, back. Yeah, and keep slowing down for EVERY crowder until you’re way below safe traffic speed. Great idea. Nearly as good as crashing into someone to make a point. :rolleyes: ---
**Author:** ![Diamonds02](https://avatars.discourse-cdn.com/v4/letter/d/b5a626/32.png) [@Diamonds02](https://boards.straightdope.com/u/Diamonds02)\ **Post date:** [January 12, 2013, 12:26am UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/116 "2013-01-12T00:26:25Z")
> [@Seanette](#): > > Yeah, and keep slowing down for EVERY crowder until you’re way below safe traffic speed. Great idea. Nearly as good as crashing into someone to make a point. :rolleyes: I seldomly have that problem with people pulling in front of me, enough for me to slow down to dangerously low speeds. I drive in the slow lane, maybe that has something to do with it. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [January 12, 2013, 1:38am UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/117 "2013-01-12T01:38:53Z")
> [@Diamonds02](#): > > I seldomly have that problem with people pulling in front of me, enough for me to slow down to dangerously low speeds. I drive in the slow lane, maybe that has something to do with it. I most commonly stay in the rightmost lane myself, and HAVE had to slow down dangerously to deal with the crowders. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [January 12, 2013, 2:17am UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/118 "2013-01-12T02:17:56Z")
Do what you got to do brother. Though this is a multiple choice question there are also multiple right answers. Some think because they get a right answer and you got a different answer yours must be wrong, that is their lesson to learn. Peace ---
**Author:** ![Flyer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyer/32/7298_2.png) [@Flyer](https://boards.straightdope.com/u/Flyer)\ **Post date:** [January 12, 2013, 6:41am UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/119 "2013-01-12T06:41:34Z")
> [@SpeedwayRyan](#): > > When I was a kid, I thought about a system that would either vary the intensity of brake lights or a wide brake light that would light only in the center for light braking, and further out toward the sides as brake pressure increased. A flashing (strobe-style) brake light when high levels of braking are detected wouldn’t be a bad idea either. The current system of the indicator being either on or off for something that can vary as much as braking level is not really a great solution. I will say that on dry pavement, you can hit the brakes pretty darn hard without ABS kicking in, so the threshold might be a bit lower than that. I don’t remember where I read it, but the variable intensity thing has been tried. It actually **increased** accidents. People got so caught up in trying to gauge the rate of slowing, that they didn’t apply their own brakes in time. ---
**Author:** ![Simple\_Linctus](https://avatars.discourse-cdn.com/v4/letter/s/9f8e36/32.png) [@Simple\_Linctus](https://boards.straightdope.com/u/Simple_Linctus)\ **Post date:** [January 12, 2013, 10:31pm UTC](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794/120 "2013-01-12T22:31:18Z")
The best courses in road driving in the world are more or less universally considered to be based upon “The System”, something developed over decades at the UK police driving school in Hendon. If you want an introduction to the system, then buy a book called “Roadcraft”. There are other excellent books avaliable but that’s the “bible” of advanced driving. When they do these courses they learn to do a commentary, there are lots of great vids of that in example on youtube or I have seen DVDs where you can watch it in example for hours. There are also lots of schools you can go to which teach techniques, as well as in the UK at least two amateur advanced driving organisations and also one semi-amateur one. Anyway here’s something I just found on youtube - I haven’t watched more than about thirty seconds of it so it may or not be terribly instructive but it has a good rating and in any case illustrates very well the commentary I am talking about. Look how systematic it is: [Advanced Driving. UK Police 999 Chris Gilbert Ult.Driving Craft DVD - YouTube](https://www.youtube.com/watch?v=bVtQ4NN5_-Q) - key thing is look how unhurried and slow/calm a true expert is when they are performing their craft properly. That’s a proper emergency high speed drive - compare it to the crazy stuff on world’s wildest police videos where the US police are sliding all over the road in crown vics… [Previous page](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794.md?page=5) [Next page](https://boards.straightdope.com/t/person-in-front-of-you-decelerates-best-to-brake-or-best-to-change-lanes/646794.md?page=7)