[efusco]

However, the 1996-2003 F-150s had a 5 star rating like the Sienna, but was an abyssmal disaster in the offset. Ford fortunately fixed the the vehicle....7 years later.

Sounds like we hit an area of interest of yours....just to elaborate a bit on your point about the 150, if I understand correctly the did 'fix' the offset problem, but they still sell the F-150 "Classic" without the sturdier structure as well. For those who don't want to be as safe as possible I guess.

I think your points should be well taken, and you're absolutely right that an SUV is not inherently 'safer'. However, in average accidents (that being rear-end and T-bone) I'll take a 3 ton vehicle over a 1 ton vehicle any day (if that's your only issue)--you just can't mess with Newtonian physics. I do love that my Prius has the 6 air bags, I always worried about those windows and support beams.
--evan

 

[petteri]

I think your points should be well taken, and you're absolutely right that an SUV is not inherently 'safer'. However, in average accidents (that being rear-end and T-bone) I'll take a 3 ton vehicle over a 1 ton vehicle any day (if that's your only issue)--you just can't mess with Newtonian physics. I do love that my Prius has the 6 air bags, I always worried about those windows and support beams.

Sure, but where does this weighty "arms race" end? There does need to be some limit to what a "regular" comsumer can buy. Driving a 3 ton vehicle on a regular basis for only its saftey to yourself is socially irresponsable and should be outlawed. If you have towing needs or other such need for a SUV than a special permit should be granted.

 

[frenchie]

I'll take a 3 ton vehicle over a 1 ton vehicle any day (if that's your only issue)--you just can't mess with Newtonian physics.

You can't mess with responsibility either. But let's be strictly scientific first, and talk about physics (I'm a physicist :wink. There are several safety drawbacks in high and heavy vehicles, like roll-over or braking issues, but to make arguments more accurate you must distinguish two cases : collision with a fixed obstacle (tree, rock, wall...) and collision with another (usually moving) vehicle.

- fixed obstacle case : a larger weight does NOT give you any safety benefit. What only matters is how smoothly the vehicle can make your body decelerate from x MPH to zero MPH, thanks to a proper (car) body design, airbags and so on. In other words, how gradually the vehicle can dissipate kinetic energy. Most off-roaders are worse than regular cars on this point, because they need a very stiff chassis for off-road purposes, and this chassis does not allow enough deformation in case of a frontal impact.

- moving obstacle case : as you probably know, there is a law in physics called momentum conservation. To illustrate it in a simple way, let's take two vehicles moving at the same speed but in opposite directions. Consider the heaviest one is moving from the left to the right in front of you, whereas the lightest one is moving from the right to the left. Because they have different masses, there is a non-zero momentum of the whole system made of the two vehicles : this momentum can be represented as a vector pointing in the right direction.

Then the two vehicles collide frontally; just after the collision they can be considered as one mass (instead of two masses having different positions before) and because momentum is conserved, this mass is still moving to the right, until friction stops it. In other words, although the two drivers were moving at the same speed before the accident, the driver of the heaviest vehicle will experience a less brutal deceleration, just because he transferred a part of its kinetic energy to the smaller vehicle.

Some people can use this argument to justify driving a heavy vehicle even if they don't need it for towing a trailer or carrying some heavy stuff. I just think the absolute opposite, and would advise these people to try psychoanalysis in order to understand why they don't feel any compassion for their human counterparts.

Physics is not the only part of the problem.

 

[patrickg]

Frenchie, Great blend of simplified Newtonian physics and social considerations. While neither hypothetical vehicle is an inelastic ball of putty and some momentum will be missing just after the "noisy part" of the accident due to deformation of structures, you have clarified the "reason" so many opt for the BelchFire 500/Abrahms tank. The greater the disproportion in relative size the less "impact" there is to the occupants of the larger unit in vehicle to vehicle collisions with generally any number of vehicles moving or not.

Of course the "problem" for the small car is multiplied in severity by the ratio of sizes as well as those occupants experience much greater accelerations which are much more demanding on their airbags and crush zones.

Now, about the oodles of air bags in small cars: Occupants of small/light cars are way safer to have oodles of airbags (than not) and my Prius Pref is air bagged to the max. Air bags help but are not "MAGIC", multi stage or otherwise. As the size of the small car's dance partner increases, the ability of the air bag to compensate for the ever increasing disparity will be lessened and at some point essentially overwhelmed. Again, it is the simple laws of Newtonian physics which are not subject to a social consciousness, political correctness, or wishful thinking.

A useful addition to Frenchies clear example is bumper/frame height mismatch. Many of the most offensive vehicles have their bumpers and frame (the main momentum transfering components) higher above the ground than with smaller cars. This greatly mismatches the crumple/energy absorbing part of the small car to the energy delivering part of the large one and often allows the small car to tend to "wedge" itself under the other's frame. This tends to slice through the passenger compartment of the smaller car with gory results.

The above is not an argument to encourage LARGE vehicles for safety but to give cause as to why certain regulatory influences that would effect the evolution of SUV's and other large heavy vehicles to be more compatible with smaller more responsible cars is needed.

Accidents happen even to the best intentioned and responsible drivers. If you are driving a MegaDeath BelchFire 500/Abrahms tank you are much more likely to inflict maiming, mutilation, and death to the occupants of another car you get into an accident with. (Even if it has oodles of airbags.) Influences that will reduce the number of LARGE DANGEROUS vehicles, casually overused, will increase public safety.



Pat