Bolt Safety

[phil0909]

The safest vehicles are the ones that are designed for safety.

Heavy vehicles are not nearly as safe. Tall heavy vehicles flip over much more easily - or more accurately, vehicles that have a Cg that is higher off the ground will flip over more easily. And they have much higher death rates than safe vehicles.
FALSE

Lighter vehicles will brake more quickly than a heavier vehicle, all else being equal.
TRUE. Of course, this is why heavy vehicles are built with stronger brakes...

Lighter vehicles have less kinetic energy at any given speed - so there is less energy that needs to be dissipated - making them safer, all else being equal.
FALSE. Lighter cars do contain less KE at a speed, but this produces greater safety only for the car/people/objects that they crash INTO. The occupants of the small vehicle itself are less safe, not more.

When a vehicle hits a stationary object, it is safer if the vehicle is lighter, all else being equal.
FALSE. Obviously false. If you drive a Yugo at a brick wall at 60mph, you will die. If you drive a heavy tank at a brick wall at 60mph, you will crash through it and survive. If the tank is heavy enough, you'll barely feel the impact. Note that 'stationary' and 'immovable' are not the same thing, and immovable objects do not exist.

TIME is one critical factor in a collision - and the total of all energy involved in the collision is another critical factor. It is the RATE of deceleration that matters - and having longer time period and having less total energy that determine the rate of deceleration, all else being equal.
UNINTELLIGIBLE.

 

[NeilBlanchard]

Phil, your opinion of my statements are mostly erroneous.

You make straw man arguments and regurgitate myths. Yugos are not safe because they were poorly engineered - not because they are light weight.

 

[NeilBlanchard]

Lighter vehicles have less kinetic energy at any given speed - so there is less energy that needs to be dissipated - making them safer, all else being equal.

The problem is that this means the deceleration forces are higher, and those are the forces that cause injury.

That doesn't matter if you're hitting a fixed object like a bridge abutment, because then it's up to the body design to gracefully dissipate momentum. A heavy vehicle can dissipate momentum just as well as a light vehicle can if it's designed properly.

But it does matter if you strike a moveable object (or if a moveable object strikes you). The heavier your vehicle is, the more energy will be transferred to whatever you're hitting (or, if you're being hit, the more it will resist that energy), which reduces the forces on you and makes the accident more survivable. This is especially important in t-bone collisions, because the brain is particularly susceptible to severe lateral acceleration.

Of course all of this presupposes an effective vehicle structure and restraint design.

Less energy means LOWER deceleration forces.

You are making mistaken assumptions about Newtonian physics. A fixed object acts as very high mass object - and therefore if your vehicle is light, then there is less energy to dissipate. Hitting another vehicle in any way other than a head on collision, it is better to have a lighter vehicle - again because your vehicle will decelerate at a slower rate with a lower peak rate.

 

[NeilBlanchard]

Lighter vehicles have less kinetic energy at any given speed - so there is less energy that needs to be dissipated - making them safer, all else being equal.

The problem is that this means the deceleration forces are higher, and those are the forces that cause injury.

That doesn't matter if you're hitting a fixed object like a bridge abutment, because then it's up to the body design to gracefully dissipate momentum. A heavy vehicle can dissipate momentum just as well as a light vehicle can if it's designed properly.

But it does matter if you strike a moveable object (or if a moveable object strikes you). The heavier your vehicle is, the more energy will be transferred to whatever you're hitting (or, if you're being hit, the more it will resist that energy), which reduces the forces on you and makes the accident more survivable. This is especially important in t-bone collisions, because the brain is particularly susceptible to severe lateral acceleration.

Of course all of this presupposes an effective vehicle structure and restraint design.

You are right about this. That's why when they show crash tests of tiny little cars and claim that minimal deformation of the cage structure shows safety, I cry for the future owners. This means all the deceleration is performed by the driver's soon-to-be-dead body.

When the baseball hits the bat, it's the baseball that sees acceleration, not the bat. Which would you rather be?

Look up what vehicles have the lowest death rates. Cars like Honda Accords and other mid-sized sedans are the safest.

Heavy and tall vehicles like pickup trucks and full sized SUV's are among the LEAST safe. They kill people by rolling over, and by not having well designed crumple structures - or that are not strong enough to absorb all the kinetic energy and still protect the people inside.

 

[phil0909]

Look up what vehicles have the lowest death rates. Cars like Honda Accords and other mid-sized sedans are the safest.

Heavy and tall vehicles like pickup trucks and full sized SUV's are among the LEAST safe. They kill people by rolling over, and by not having well designed crumple structures - or that are not strong enough to absorb all the kinetic energy and still protect the people inside.

Neil, you are simply wrong. If you had clicked my earlier link on safety by model and size, you would already know that you are wrong. The best-researched lists of safest vehicles - both for injuries and deaths - are dominated by trucks and SUVs, not mid-sized sedans. Small cars have the highest rates of injury and death.

You have convinced yourself that you are smarter than anyone who disagrees with you. In fact, you are not. If your mind remains closed, you will continue to be incapable of learning. Or participating in an intelligent discussion.

https://phys.org/news/2015-05-heavier-pricier-vehicles-safer.html
https://phys.org/news/2015-01-vehicle-highest-lowest-death.html#nRlv

 

[SeanNelson]

Lighter vehicles have less kinetic energy at any given speed - so there is less energy that needs to be dissipated - making them safer, all else being equal.

The problem is that this means the deceleration forces are higher, and those are the forces that cause injury.

That doesn't matter if you're hitting a fixed object like a bridge abutment, because then it's up to the body design to gracefully dissipate momentum. A heavy vehicle can dissipate momentum just as well as a light vehicle can if it's designed properly.

But it does matter if you strike a moveable object (or if a moveable object strikes you). The heavier your vehicle is, the more energy will be transferred to whatever you're hitting (or, if you're being hit, the more it will resist that energy), which reduces the forces on you and makes the accident more survivable. This is especially important in t-bone collisions, because the brain is particularly susceptible to severe lateral acceleration.

Of course all of this presupposes an effective vehicle structure and restraint design.

Less energy means LOWER deceleration forces.

Read more carefully - you are talking about kinetic energy and impacts against fixed objects, I'm talking about g-forces on the occupants and impacts against moveable objects.

In terms of injury, it's the g-forces on the occupants that count (as well as restraint design and cabin intrusions), not the mass of the vehicle. And the g-forces depend on good vehicle design no matter what the mass of the vehicle is - and, in the case of hitting moveable objects, the relative difference between the masses of the objects. The heavier the vehicle, the less g-force it will experience when hitting a moveable object.

 

[marshallinwa]

Here is what the iihs says:

http://www.iihs.org/iihs/news/desktopnews/new-crash-tests-demonstrate-the-influence-of-vehicle-size-and-weight-on-safety-in-crashes-results-are-relevant-to-fuel-economy-policies

http://www.iihs.org/iihs/topics/t/vehicle-size-and-weight/qanda#vehicle-size-and-weight

The good news is that small cars are much safer then they use to be. So that crash in the Yugo that sent you to the pearly gate may be survivable in a Chevy Bolt.