The California Driver's Handbook says...
> California’s “Basic Speed Law” means that you may never drive faster than is safe for current conditions.
> You must drive slower when there is heavy traffic or bad weather. However, if you block the normal and reasonable movement of traffic by driving too slowly, you may be cited.
https://www.dmv.ca.gov/portal/handbook/california-driver-han...
The Tesla, FSD or not, blocked the flow of traffic and was partially at fault. The vehicles behind the Tesla were driving too fast given the conditions and were also partially at fault.
The handbook is structured to minimize the chance/danger of accidents even if other drivers aren't adhering to it.
You could ram the other vehicle. In that case no amount of safe/defensive driving would stop that.
But a safe/defensive driver will go as slow as you do if you merge in front of them.
If you exceed the traffic of the lane next to you, you will have low "following distance" to it, and a deceleration disadvantage. Plus, humans have reaction times.
If their vehicle is fully in the lane, I'm almost certainly going to be completely at fault.
I'm no expert in US law but I think there's probably at least a dozen separate laws on what is (il)legal, and I'd bet it's more than the 8 paragraphs in the source you linked to
But the nothing can instantly stop, it's physics. The recommendations, at least in Germany are so that you have enough time to react + brake if the car in front of you does an emergency braking manœuvre.
If the car merges into your lane at too little distance, like here, you have to slow down. A lot of people don't.
A car striking a pileup in front of you can come pretty close, though.
That explains a two-car collision. The following pileup is explained by drivers not leaving enough space to react and brake.
The rest of the pileup is varied. Some of it is from too short following distances or really lack of reaction.
Some drivers in the back had no ability to see the pileup ahead and had cars stop in front of them (from dissipating their energy in a collision) in less distance than they could brake.
In other words, these drivers did not leave enough distance to react and brake.
Again, recommended following distance is ~250-300 feet when stopping & reaction time can be 350-400 feet. This is OK when the car in front of you brakes, because you'll both be decelerating with a similar profile and you'll have more than 250-300 feet to stop. It is not OK when the car in front of you stops substantially faster than braking with no warning because it has hit an unknown obstacle.
assuming you are in California: https://www.dmv.ca.gov/portal/handbook/california-driver-han...
operating a motor vehicle in the United States requires that you have this entire booklet (or that of another state; they are all nearly identical) memorized, cover to cover.
* The 3 second rule I cited: "To avoid tailgating, use the “3 second rule”: when the vehicle ahead of you passes a certain point, such as a sign, count “one-thousand-one, one-thousand- two, one-thousand-three.” This takes approximately 3 seconds. If you pass the same point before you finish counting, you are following too closely." https://www.dmv.ca.gov/portal/handbook/california-driver-han...
* Real-world stopping distances being longer than 3 seconds (3 seconds * 55MPH = 242 feet) -- "Assuming you have good tires, brakes, and dry pavement: At 55 mph, it takes about 400 feet to react and bring your vehicle to a complete stop."
If someone dives and brakes in front of you, with a slower starting speed and equivalent or better brakes: you're a-gonna hit them. And no one seriously proposes that you should never drive faster than the lane next to you, which would be the only way to avoid this.
The car departed the lane next to them, dove in front of them, and stopped.
Do you always leave enough space so that a vehicle in the lane next to you can do this?
> if you are so close that you can't stop in time in that situation, you are following too closely. end of statement.
> yes that does happen to cars, by the way. a car driving at speed X which hits another car head-on at speed X will cause both cars to come to a complete stop, instantly, provided they are the same mass. usually they are not the same mass, so that car which you were following could suddenly not only stop, but change direction and accelerate towards you.
Recommended following distances are nowhere near "instant stop of vehicle in front of you plus reaction time". E.g. California recommends 3 seconds of distance at your current speed-- 286 feet. Real world stopping distances are often ~300+ feet, after 100 feet+ of reaction time (yes, I know that vehicle tests in ideal conditions often achieve something more like 150 feet not including reaction times).