Do we really need all that safety stuff?
Altough it seems negligible, seatbelts and airbags do add some weight and, considering airbags and pre-tensioning seatbelts, some complexity that seems a little too much for me. I wouldn't mind if I could have lap-belts in a new car for a lower cost instead of 3-point belts, and considering that American school buses don't have seatbelts but are still deemed the safest terrestrial vehicles in the world would we really need airbags and seatbelts?
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How many people do you know that got killed or hurt in traffic accidents?
How much better would they have fared if their cars were up to spec in safety, or how much worse if not? I made the tally and I cherish those safety features, I don't mind spending a few drops of fuel extra to carry them around. I was a passenger on a city bus that rammed a car at about 10 km/h. Many people in the bus fell. Some got hurt. |
If I drove a school bus, I wouldn't wear a seatbelt either. I drive vehicles that are less than the average weight in America, so I wear a belt.
I wonder how much weight all the airbags and related systems add? I have front, knee, and side airbags in the Prius and TSX. That said, I also ride a motorcycle, which means I am comfortable with the danger of having no restraint system, let alone car frame. People in the U.S. tend to be very paranoid about safety. When I asked about buying a reconstructed titled car on the Prius forum, most people thought I was crazy to even consider it. In their mind, the car could explode at any moment. Some will buy a large SUV for safety reasons, yet statistics show that we will most likely die of heart disease. If people were truly concerned with safety, they would eat less and exercise more. |
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Example, a Metro weighed in at ~700kg, while current cars of that size are often weigh over 1000. That's before we account for the way modern vehicles are built, where weight is carefully kept to a minimum. If you built a Metro with modern techniques (to the same crash standards), it could weigh as little as 500kg, and even less if you went with some of the more exotic materials that are now creeping in. A 500kg car would stop in far less distance than a 1000kg one, and if you consider that 5 metres of stopping distance is the difference between stopping safely and having a severe accident, it's hard to say that safety technology does anything more than make you feel safe (which probably makes you less safe). |
Breathing causes Cancer.
If you don't think that is true then just quit breathing. I guarantee you will NOT die of cancer. Point is you can argue any point well enough to give it some validity. The wife thought I was crazy to buy the Sentra. "It doesn't have airbags!" But dear it has automatic shoulder harnesses so I will never get a ticket, even if I forget to wear the separate lap belt. Going back to the era of the 50s and early 60s, I can only wonder how high the road fatalities and permanent injuries would be without. windshields that don't decapitate people Side guard beams that prevent terrible injuries in minor collisions collapsible steering columns instead of spears decent brakes versus, oh my god the pedal just went to the floor! recycling crankcase blowby instead of a cloud of smoke identifying traffic jams tires that last more than 6k miles regards mech |
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If a car is twice as heavy it will press twice as hard against the road; the tires can generate twice as much friction before they begin to give way. A car that is twice as heavy should, all other things being equal, be able to stop in the same distance as a lighter car. Of course the brakes need to be able to handle twice the braking force too. If you fail to brake in time then the damage inflicted will be higher, that's true. On the other hand, if you get hit you'd better be in a heavier vehicle as the higher mass of your own vehicle makes the resulting speed change after impact lower. But stopping distance and vehicle mass are totally unrelated to each other. |
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A smaller car would feel more nimble, as it has a smaller footprint so it reacts (rolls) more to changes in direction or speed than a big car would. But that's relative to its size, not absolute. There are big differences in suspension setup between cars. That alone may cause your Leaf to feel heavy compared to the Prius. Most high performance sports cars are heavier than either, but nobody would say they are less agile. |
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They'd be too heavy for that light car otherwise, too much unsprung weight for such a light car. They'd be cheaper to buy, there you have a point. |
as well as extra weight is a handling liability in slippery conditions, so many corners in the leaf where I'm left wondering it is ever gonna stop sliding and start turning :) Where a tercel would have long since straightened out and been accelerating for a spell, even on cheap tires.
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My MB100 had this issue, it was front wheel drive and the front of the engine say a good three feet from the front axle centre line. Nothing but plow on understeer there. I did manage to get the back to step out a little once, by braking hard mid corner. :thumbup: |
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Weight helps break the thin film of water on wet roads. My '85 Civic forced me to slow down on rainy days, it would aquaplane at speeds as low as 50 mph. My much heavier Nissan Almera never aquaplaned at all, nor did my Insight. Friction increases with mass... Quote:
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At the end of the day all engineering is a compromise. In competent hands, a light car could be every bit as safe as a gimzo ladden pig. |
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Tires are much better nowadays, definitely.
When I got Michelins on the old Civic much of the aquaplaning was gone (not all) and it did corner faster. But the Civic was a very light car with relatively large wheels. The Insight is over 50% heavier but its tires are just 2" taller and 2 cm wider, that is about 20% more thread on the road. Tire pressure is higher too (even OEM) |
Strange, the only car I ever experienced hydroplaning on was a giant buick. I would guess wider tires are disproportionately more likely to hydroplane since any edge effects are minimized.
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https://www.google.com/webhp?sourcei...20seat%20belts |
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I'm H2O intolerant!
When I learned to drive a school bus, they always emphasized situational awareness (once I joined the Army, I forgot civilian terms), because if we needed to slam on our brakes, we very well might not be able to stop in time. We had a driver suspended because a woman cut him off and slammed on her brakes. He could not stop in time. There were times that a light turned yellow and I left a skid mark going through the intersection. The big trucks that I drove did not have good stopping distance, either. They always said that school buses are safer without seatbelts, but if the students are properly seated, they will be bouncing off a padded seatback, instead of flying into the steering wheel and windshield. However, accidents involving school buses are not limited to hitting something at the 12 o'clock, or something hitting our six; if something side-swipped us, the passenger would be bouncing off of each other and the opposite side. With the high center of gravity, there were many more possibilities to contemplate. My district only had "transit-style" buses, where the engine was next to the driver--nice and warm, whether you want it or not. Loud, too. I always thought that I might like a nice and large engine compartment between myself and an equal and opposite force instead of, in my case, a metal dashboard. |
I don't mind the safety features I just don't have think the government should mandate them. I think the consumer should be allowed to choose their own level of perceived safety.
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They do. That's why we have SUVs, because they're safer.
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How many of those safety devices are found on a typical motorcycle? |
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http://youtu.be/d7iYZPp2zYY |
TopGear UK had a short, but relevant test on this weeks episode. They wanted to see how fast a common car, the Vauxhall Insignia, would need to be travelling to require the full stopping distance (315 feet) at 70 mph.
The answer? 112 mph. That's a huge increase in Kinetic Energy over 70 mph. People also seem to neglect that you can't always avoid an accident. You might avoid hitting the stopped car in front, but the person behind might not avoid hitting you! Quote:
And let's not forget, some of these systems do the braking for you. Automatically. My friend believes his Merc's auto-brake actually avoided an almost inevitable accident because it was able to apply the brakes harder and faster than most drivers. |
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Complexity? Yes, all that computer control!
Weight? Yes, but not a huge amount. Cost? YE$, too damn much! |
My Celica has a driver side airbag, ABS, side-impact bars, and safety glass. Looks fine to me :-)
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Keeping in mind the Caterham is something an average DIY mechanic can build from scratch and doesn't have ABS, EBD, brake assist etc, that the others do. Porsches have always stopped quickly because the rear weight bias controls weight transfer under heavy braking. Think about it this way, you're out on a drive and for whatever reason you need to stop suddenly (you happen to have 43m to do it), the dangerous light weight car stops without a scratch, while the safety ladden Cruze sends you to the hospital and probably the morgue. There are of course some unavoidable accidents, but in general good handling/ braking cars could reduce accident severity at least as much as passive systems. I wonder what would happen to the road toll if governments gave manufacturers the option to build actively safe cars in return for lower crash requirements. It seems like safer cars don't translate with any significant meaning to reduced death and injury statistics. |
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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. :p It's something many people get completely backwards .. mostly because some of the figures taken by themselves can be misleading. So here goes :rolleyes: 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. |
I see crazy drivers every day. I drive through 3 very accident prone intersections twice a day. I also do a fair amount of city driving when I go to college 2 days a week.
I'm married with a 2 year old some and another on the way, safety is important to me. Yes I drive carefully, I have even had smith driving classes but that doesn't protect against crazy scenarios and idiot/drunk drivers. Personally, give me all the safety equipment possible. On that same token, I do wish cars weighed less. I think with CAFE standards vehicles will get lighter, but the days of 1500lb(700kg) cars is long gone. |
lol, married with kids as excuse for driving 3800 lb car, emotional, completely misses the point.
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Don't forget to put a "Baby on Board" sign in the window- you know, so I smash into anything but that vehicle.
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Design geometry and material strength are key to crash safety. Good braking and handling are key to accident prevention. Safer drivers in safer cars means fewer fatalities. When air bags first came out people were afraid of them. Now we know how well they work. The only downside is that nobody smokes a pipe in their car anymore.
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Anyone ever take note of how much baby seats resemble racing seat setups? How about bolstered seats and 5point harnesses in every car? Maybe a comfortable bike helmet that works with a HANS device to not limit visibility or effect comfort of the drivers? Shouldn't we all be driving tube chassis race cars anyway?
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The "road-hugging weight" ads from the 70s were pure BS. Lighter cars corner harder, brake shorter, and accelerate harder than heavier ones--given the same tires, brakes, engines, etc. -soD |
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