Hacker News Reader

Comment by merraksh | Hacker News Reader

What puzzles me here is that the SUV flips over after being hit in the right-rear corner by a relatively small car and bumping into the side barrier. Flipping over in a case like this looks more likely to happen to an SUV than a lower-centered car, and makes me question the safety of SUVs.

View on HN

SUVs are not as stable as cars with a lower height. Think about the typical race car which is designed for turning fast, something that requires stability: light, low and wide. SUVs? Heavy, high and narrow relative to their height. Electronics can do marvels, but with the same electronics physics wins.

I remember I could easily outperform a couple of BMW SUVs on a highway in a descent from a mountain pass. They had passed me on the way up, more HPs and gravity helps handling. Then I kept turning at 130 km/h on the way down, where gravity is detrimental to handling. They were suddenly much slower, especially one of them (a prudent driver, I guess).

I'm really curious to know exactly where you can legally drive downhill at > 100 km/h

It's the standard speed limit on highways in Italy. It can be lower when the road or its conditions suggest prudence.

It can also be 20 km/h faster on wide straight roads but I still have to see that. I guess nobody is risking the bad press after the first accident at 150 km/h.

In the US, especially out west, 75-80mph (~130km/h) is commonly set as the legal speed on most of the freeways.

The Coquihalla highway (BC-5) is notorious for it's steep hill and the speed limit is 120 km/h in ordinary conditions. I could probably find a lot of highways in BC that are similiar.

I came down I-70 into Denver one time in a rented Ford Expedition. Wasn't going that fast, but when I hit the first curve, the body and frame started to really lean onto the outside suspension. I was scared to hit the brakes and cause it to pitch more, so I just barely touched them and had to let it drift into the next lane a bit. The turn went on forever!!

Did I mention I was surrounded by motorcycles?

Luckily you handled it right.

On the very same road I wrote about, I've been driving another car that couldn't turn at 90 km/h uphill without drifting outside. It was not a SUV. Suspensions setup is very important for safety: a car that can turn fast is a safer car. I tested an Audi TT on ice at low speed (ice tires) and it was like turning on asphalt. Other more normal cars, not really.

A more extreme, but related condition is a "moose test":

The dangerous Toyota Hilux:

https://www.youtube.com/watch?v=xoHbn8-ROiQ

The Jeep Grand Cherokee acting similarly dangerously:

https://www.youtube.com/watch?v=zaYFLb8WMGM

It would be appropriate to list the model years there, especially if other years have solved the problem!

The Hilux video title says 2016 -- same issue remains as in 2007.

Interesting to see the Jeep blow the front left tire... 7 times. Consistent.

Hitting the brakes hard is typically the first instinct, but is rarely the correct course of action. Ice is also something that afflicts drivers in Colorado.

This is a commonly known problem of SUVs, their center of gravity is a lot higher so they're a lot easier to flip over. That's why I'm puzzled by people who buy urban SUVs, that is, jeep-like cars that they never intend to use off-road.

Quite often they're a fashion statement more than anything else.

Transporting a family takes room. Rear facing car seats don't necessarily fit into smaller cars.

Large sedans and station wagons are valid alternatives; SUVs are similarly or higher-priced.

Large sedans and station wagons are valid alternatives; SUVs are similarly or higher-priced than safer options.

Height is the big advantage of SUV's and minivans. Kids stay in carseats much longer now and the seats can be quite bulky. It's a lot easier to load them into something with some height.

People like the visibility from sitting higher. Also, "bigger = safer" is a common thought process.

Also people get old and want a car that they can get in and out of without having to lift/drop their own centre of gravity.

Ride height, more cabin space for kids, some use for four wheel drive if you live in a climate with snow/ice, and/or personal preference?

I currently drive a civic so am just guessing...

1: Station wagons that seat more than 5 people basically don't exist anymore (last I checked only the Mercedes Benz could do so in the US).

2: Minivans have an image problem (still associated with the "soccer mom" stereotype for Gen X; millenials appear to be less averse to them). In addition, most minivans are elevated so that they can have a flat floor, so they similarly have an elevated center of gravity.

Bringing it back full circle, the Tesla Model S can also seat 7, as long as two are children (and you buy the option for third row seats).

Yeah, if I was willing to drop $90k on a car that would have been an option. The E-class station wagon is cheaper, but still more than we were looking at. The Mazda 5 was an amazing car, but is now discontinued in the US, meaning there are now no compact cars that can seat 6+.

I didn't realize the Mazda 5 was discontinued. Too bad, it looked like a pretty practical design.

> Minivans have an image problem (still associated with the "soccer mom" stereotype for Gen X; millenials appear to be less averse to them).

Might be that millennial perception you're talking about, but I always thought soccer moms drive SUVs.

They flip over easier but they are more heavy, which is safer in crashes. In a head to head crash between a car and an SUV, the SUV is significantly safer. I believe SUV's have lower fatalities per mile driven.

> I believe SUV's have lower fatalities per mile driven.

I would be interested to know how this compares with other vehicles if 'fatalities per mile driven' included fatalities that involved non-SUV occupants.

Is the assumption here (flipping over = very bad) correct? Is it possible that [edit: the force] can dissipate more easily if it flips (provided the car is built correctly to withstand the force of a flip)?

NB: I know nothing about this topic, genuinely curious to hear from someone who does.

> Is it possible that can dissipate more easily if it flips

They may have more structural material, but they're also heavier, meaning they have to absorb more energy.

I'm genuinely curious about this too. In my uninformed opinion, for a car that's heading toward an obstacle (e.g. car, truck, pillar, wall, lamp post) there are a few possibilities:

1) heading straight while braking: probably the best case as you have the collapsible trunk between you and the obstacle, and you can reduce the speed, if by little;

2) spinning without control and crashing with the back or the sides: worse than 1), but not so bad as there are side airbags and the headrest. The car is at least somewhat protected on all sides, plus there's some tire friction for reducing the speed;

3) rolling over: less friction as the car is rolling, plus the car may crash into the obstacle with the car's roof or floor. Both are certainly more than a layer of tin, but not as protected. Plus, objects flying around the car and limbs in an unsafe position when the crash happens.

I think you're on to something. The people in the small car were almost certainly harmed a lot more than those in the SUV. Just look at how hard it slams into the SUV. Provided the seat belts are able to hold the passengers in the SUV in place, I think they survived without much harm. I'm more worried about the passengers in the small car.

Small bump: http://www.ed.nl/polopoly_fs/1.6785912.1482854466!/image/ima...

Ouch: http://www.ed.nl/polopoly_fs/1.6785892.1482854220!/image/ima...

Source: http://www.ed.nl/regio/valkenswaard-e-o/valkenswaard/video-d...

Modern cars are incredibly goo at absorbing shock from the front and rear directions. They are much worse on any other direction, wether it is lateral or vertical. The flipping means everybody in the car had a huge shock the first time it felt, probably worse than anything people suffered on the other car.

Flipping also does not help stopping faster (in case there's something dangerous ahead). Instead, the faster way to break is by using the wheels just like the car is designed to do.

Reply on news.ycombinator.com