One-way high-speed highway: brake to slowdown. The worst thing than can happen is someone will rear-end you.
Two-way street: brake to slow or stop.
Changing lanes is a bad idea. What if the idiot in front of you is slowing down to make a turn? By changing lanes you could be headed for a wreck as he also turns.
I pump my brakes a few times to make the brake lights flash and then brake as necessary to avoid the car in front of me.
Unless the preceding vehicle had just slipped in front of you, and then immediately braked, you certainly do have this control.
And I agree with your wife.
The cognitive load of executing a lane change is tiny, excepting some notably bad weather or traffic conditions.
And the grace argument doesn’t necessarily have anything to do with other drivers. Sudden hard braking is physically disruptive to me in a way that competent, fluid maneuvers are not. If there is other traffic around, braking below the generally prevailing speed makes lane changes harder and riskier. You get stuck as faster vehicles from behind make the change and zip around you; you have hitched yourself to the guy in front.
The very first thing you do is step on the brake. You don’t slam the brake down, you need to make sure who is behind and beside you, and in a split second decide whether to press harder on the brake or change lanes. Once you know that the conditions are acceptable for changing lanes ( mainly that you are not trying to put yourself and something else in the same place at the same time), then you can change lanes. And it is a good idea to change lanes if you can because your car may take longer to stop than the one deaccelerating in front of you. But if you can’t change lanes you are going to have to step harder on the brake, accounting for road conditions like rain, snow, rough pavement, etc.
The problem with only braking in that situation is that you may be deaccelerating too rapidly for someone behind you, and if you only do it reflexively you may not take proper account for the road conditions. You also may not be able to stop in time and you will run into the car in front of you when you could have gone around.
But no matter what you should immediatly begin to brake. This will start slowing you down, and your brake lights will alert everyone behind you that something unusual is happening.
In the very artifical OP, where you have no idea what is to your side, yes you should brake. And brake hard at that.
In practice, an excellent driver like me will know what is surrounding me and will have an idea that the vehicle in front is going to slow down for some reason. So in anything other than stuff coming to a stop in all lanes, either I will have slowed down by engine braking way before or will be in another lane.
Except in literal stop-start traffic, you should probably only be touching the brake about 1 in every 500 miles on highways/motorways.
You should touch the brakes any time that is the best course of action. There is no number of times per mile to gauge that by.
I am not suggesting that you drive without the brake for 499 miles then hit it.
I am just estimating a rule of thumb. If you hit the brake more often than that on general highway mileage then you are probably not driving very well and should seek to improve your competence.
There’s no rule of thumb. Traffic and road conditions vary too widely. You could find an average for the conditions you drive in, but it doesn’t apply to others.
I don’t think DH or I ever noticed that on visits to LA (we never lived there), but it’s ubiquitous in Sacramento, plus all the annoyances mentioned by olives as common in NJ.
But if you are about to change lanes, slowing down may be exactly the wrong thing to do.
He did apply his brakes.
I’ve noticed it in LA.
I can absolutely confirm that this is par for the course in Sacramento. Even my 14 yo son remarked on it happening the other day when we were driving on I-5 through town.
It’s interesting that there are people on both sides here, though the general consensus seems to be in favor of braking.
I don’t think there’s such a thing as knowing what’s around you at all times. You’ve got so many different spots to look at in order to determine everything around you that by the time you’ve checked them all you can’t be confident things haven’t changed unpredictably somewhere.
My wife also talks about this kind of awareness. I don’t think she (or anyone else–sorry I know that’s a little rude) has it. I think there’s a failure to know one’s own epistemic and cognitive limits here.
But having said that, if you do know at all times what’s all around you, then sure, changing lanes can definitely make sense in this situation. I just don’t think anyone knows at all times what’s all around them.
(For the record I have a much better driving record than her. However neither of us has been in an accident in nearly a decade. Prior to that, however, I was in a fairly serious one at the age of 16, and then a very minor fender bender in my mid 20’s. She, on the other hand, had been in like six collisions or something. I attribute this to her thinking she’s more aware than she actually is. However I don’t (any longer) attribute this to her within earshot. 
)
I know it’s common for people to think they’re a better driver than they actually are. 
I’ve been driving vehicles for almost 40 years. I’ve driven in three different continents (including quite a bit in the UK, on the “other” side of the road). I’ve driven in Turkey, Greece, Costa Rica, all over Europe, Israel and Egypt. I have tended to be the primary driver whoever I’m with. I’ve always commuted, and have lived in states where there’s a significant snow season since 1985. I drove a semi all over the country for almost three years, probably averaging 8,000 miles a month. And I drove a bus for a while, long ago. I’ve driven a LOT; different vehicles in all sorts of conditions.
And my one and only at-fault accident was a year after I started driving; I was 18. Not even a fender-bender since 1976. And I know for a fact I’ve avoided quite a few. My last speeding ticket was two months ago :mad: but the one prior to that was…1995 or '96.
So, yes…I believe I am a better driver than most people, with a 40-year record to prove it. /brag
And while it’s certainly true that nobody can be aware of every split-second move by other drivers, especially at freeway speeds on a multi-lane highway, I maintain that it is possible to be aware of all the cars around you and what they’re doing - or going to do - almost all the time, and this is crucial to being a safe and accident-free driver.
I check all mirrors about every five seconds as well as paying attention to what’s happening way up ahead of me. For me, driving is very active; I’m not just looking, I’m paying attention and thinking about what I’m doing. I think if you were to poll people with very good driving records, you’d find this to be a common trait.
If you’ve been driving with due care and attention, you’ll have been checking your mirrors and should probably already know whether it is safe to change lanes.
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.
What “other things” than being aware of what’s going on around you while driving are more important to do while driving?
It doesn’t take much cognitive energy to check mirrors and pay attention to the task at hand…
That reminds me of another common beef she has with my driving. I tend to signal in circumstances where she doesn’t think I should. She thinks if it’s independently obvious where I’m going, there’s no reason to signal. But I signal pretty much every time I’m going to turn the wheel a considerable amount, for whatever reason. This drives her nuts.
But I say it’s a bad idea to have to think out “is this a situation where I need to signal?” and instead it’s a better idea simply to have the habit “when I’m going to turn the wheel a substantial amount, signal beforehand.”
So if I’m in a turn only lane, I signal. (I think you’re really supposed to do this anyway but she seems to think otherwise.)
If I’m in a parking lot, I signal when I am going to turn (Again–I am pretty sure you’re supposed to do this, but she seems to think otherwise.)
But also, if I’m on a road which takes a sharp turn at some point, I tend to signal. (This I know is not required, and it’s the one that really makes her mad.)
What harm could I possibly be doing in that situation? None whatsoever that I can see. And by simply making it a habit to signal whenever I’m going to turn the wheel substantially, I free my brain up to think more clearly about more important things about the driving situation.
Again, what I am saying is that constantly checking your mirrors does not give you the kind of awareness you’re saying it does. It is best to check because you have (in many cases anyway) no idea what has happened in the second since you last checked.
If I’m thinking about whether I need to check or not, I’m not paying attention to the road situation around me. That’s my point. Simply having the habit of checking is how to be as aware as possible of the road situation around you.