I've learned the hard way not to expect anything from other drivers on the road.
Make sure your following distance is such that you have enough time to react to completely oblivious driving behaviour from other drivers.
While I fully endorse this ideal, the reality of driving in high-traffic cities is that it's impossible. Every time you adjust to leave proper space, someone will come along and appropriate your safety buffer. When you slow again to allow enough space, the pattern repeats.
As others discussed throughout this thread, there are many situations where drivers violate the safe following distance rules. Aside from the lack of attention scenarios, I think many drivers take calculated risks to temporarily reduce their following distances while performing some other maneuver. They should incorporate this new idea of neurotic automatic-braking systems into this risk calculus, so they don't get caught in a situation they cannot handle.
While we have a mixture of different vintage cars (and drivers!), I am afraid we will remain living in interesting times...
You also give yourself a buffer when vehicle ahead have an emergency stop - imagine there’s a truck behind you.
I guess what I’m saying is these ‘brake checks’ are welcome, even if they only serve to educate people.
If you leave a large enough gap with the car in front, then people will merge into that gap. If you then slow down to create a new gap - people will overtake and merge in again. You end up travelling slower than the rest of traffic, with people overtaking and merging, which creates dangers in itself.
There are three scenarios if I'm not overtaking:
1) I'm going faster than the vehicle in front. In this case, it doesn't matter if another vehicle pulls in between us because I'm about to overtake anyway.
2) I'm going slower than the vehicle in front. In this case, it doesn't matter if another vehicle pulls in between us because I'm falling back and the gap is ever-increasing.
3) I'm going approximately the same speed as the vehicle in front. In this case, there tend to be two ways a vehicle pulls inbetween us:
a- it's merging from an on-slip-road (on-ramp?), in which case this doesn't happen often, and I'll just fall back or overtake b- it's just overtaken me, then slotted into a gap that's too small for it anyway. If the car has overtaken me, it's mostly because it wants to go faster (in which case it will probably vacate the space again soon) or it wants to pull off (in which case it will definitely vacate the space again).
If I am overtaking, then yes, someone may pull into the gap, but I'm still overtaking the vehicle I want to get past.
If you stop worrying about going 2mph faster than another lane of traffic, then leaving a safe gap is mostly pretty easy and stress-free. It will only take you 15 minutes longer to drive 200 miles at 65 than at 70.
c- a vehicle in the lane to your left that you were going to overtake has itself caught up with a slower vehicle and wants to pull out to overtake it, moving into the gap in front of you
d- a vehicle with an impatient driver is undertaking traffic (passing to the left of slower vehicles) and then moves into the gap in front of you.
The first of these is a normal situation, but still results in a vehicle moving into the space in front of you, sometimes without accelerating up to your speed first. Fortunately, it's usually easy to anticipate this situation, and many drivers will helpfully drop back a little to allow more space for the other vehicle to move out.
The second of these is a result of aggressive and probably illegal driving, and is more of a problem because the driver cutting in may well be going too fast, move out into a space that isn't really wide enough, and then brake suddenly.
Still, in my experience these don't cause much delay if you're allowing a sensible gap in front. I find people who try to keep closer to the car in front to deter others from pulling into "their" space seem to get far more upset about these situations than I do.
Reminds me of the George Carlin line: "anybody driving slower than you is an idiot, and anyone going faster than you is a maniac"
In Germany, this is legally required. However, the safety distance is often abused by other vehicles when passing.
Unless the tailgater also has this system!
You don't erase the standing wave by having everybody maintain a fixed following distance or mimicking the speed of their leader. You need to predict future changes and allow the space to contract to help smooth out the transient disruptions and slowly rebound without over-shooting. You want each following car to react less than the previous and have a weaker deceleration/acceleration curve.
Unfortunately, I have noticed increasingly absurd feedback loops in long distance routes here in CA. As a user of conventional cruise control, I can't help but notice how frequently I now have to intervene to adjust speeds in relatively light traffic conditions. On long drives like LA-SF via I-5, these yo-yo drivers are my new nemesis. I don't know if it is due to their use of adaptive cruise controls or a more basic loss of attention or self-awareness. For example, I see packs of cars with speeds oscillating between 55-80 MPH when conditions should easily allow a steady cruise at 75 MPH.
One of them thinks I will drive into a wall when I’m approaching a 90degree turn with a wall. Does the break check from time to time. Nothing weird at high speeds for now.
Other had a single break check at high speed, there was nothing in front so the sensors somehow messed up I guess. It braked for something like 100ms, at least it felt like that. Then kept driving normally. But even that was scary.
This is to persuade you to also buy a car with new brake tech ;)
You've just explained why autonomous braking is completely unnecessary. People are perfect, never make mistakes and never assume that the car in freely-flowing traffic ahead of them won't stamp on the brakes for no apparent reason.