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Old 02-11-2015, 07:36 PM   #33 (permalink)
IamIan
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Sorry ... but ... no ... all else being equal the larger heavier vehicle is inferior to the otherwise equal lighter vehicle... for breaking / stopping ... and for cornering.

#1> tire/road friction doesn't necessarily increase with mass ... ie the component of your mass that acts perpendicular to the road surface ... the 'normal' force .. is what increases the tire/road friction ... ie you have less tire traction/friction (but same mass) going up or down hill.

#2> However .. no matter what the angle is .. up hill or down hill .. momentum always increases with mass.

All else being equal... A heavier vehicle has to take a longer distance to break going down hill ... due to angle , it has less 'normal force' thus less road/tire traction/friction ... but it's momentum from the higher mass is still just as much higher .. and the additional mass means it has a greater gravitational pull downward as well.

Down hill ... all else being equal ... Heavier vehicle always at a breaking disadvantage/penalty.

- - - - - -

the ... 'all else being equal' ... part is the only way that engineer's can try to compensate for the higher mass automatic penalties .. by investing in bigger/wider tires, bigger brakes, etc.

But .. a lighter car can also be engineered with those wider tires .. bigger brakes , etc ... thus it can get those benefits and have less mass to brake.

If anything the finite limits of materials put the larger / heavier vehicle at a scientific and engineering disadvantage ... as far as trying to scale up and keep pace with the increased vehicle mass ... The same thing happens to larger buildings .. and why an ant wouldn't be as proportionally as strong if it were the size of a house... ie there are automatic and unavoidable penalties to scaling up.

- - - - -

And just for fun ... even if we want to ignore all that ... statistically overall if you lump it all together ... for whatever reasons you might think are the cause ... generally one is more likely to die driving a heavier vehicle than a lighter one.

It's something many people get completely backwards .. mostly because some of the figures taken by themselves can be misleading.

So here goes

First ... what are all those safety requirements worth ? ... big or small vehicle ... they save lives... total death rate per billion miles vastly decreased over time as we implement these features.

Now the one graph seems to look like the heavier vehicle's have lower rate of deaths ... it looks like a decreasing rate of death as vehicle weight increases ... but look closer.

The Numbers:
In 1988 vehicles 3,500 lbs and over had on average 100 deaths.

Same year 1988 vehicles 2,500 lbs and less had on average 150 deaths.

Sure 150 looks bigger than 100 ... and that makes it 'look' like the heavier vehicles were statistically safer ... but ... it becomes a question of that other part of the description ... per million registered vehicles ... that's important.

Because when we look at the other graph ... to see what the distribution of that 1 million registered vehicles was for that same year ... out of every 1 million registered vehicles 150,000 were 3,500 lbs or more ... but ... 500,000 of them were 2,500 lbs or less.

So out of every 1 million registered vehicles in 1988.

150,000 vehicles (3,500+ Lbs) had 100 deaths = Death rate of 1,500 vehicles per death.

500,000 vehicles (2,500- Lbs) had 150 deaths = Death rate of 3,333 Vehicles per death.

For whatever reason you like ... those driving 3,500+ Lbs vehicles were twice as likely to die as those driving 2,500 lbs or less vehicles.

No .. I didn't just make up numbers ... reputable reference source used for and sited on each graph.
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