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Old 2014-08-19, 07:51   #12
xilman
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Default Unintended consequences.

After wearing crash helmets when riding a motorcycle became compulsory in the UK, the number or paraplegic or quadraplegic ex-bikers rose significantly.

People tend to survive longer with a broken spinal cord than with a markedly re-arranged brain.
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Old 2014-08-19, 13:05   #13
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Quote:
Originally Posted by retina View Post
I am confused as to how a car seatbelt can make pedestrians safer. That just doesn't make sense to me. I think there are some flaws in such studies that claim external parties are safer because of seatbelts. But if I am wrong about that I would like to see an explanation as to how such effects are manifested.
IMO it would come from the fact that as well as going faster the seat-belt allows for quicker application of brakes.

Last fiddled with by science_man_88 on 2014-08-19 at 13:13
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Old 2014-08-19, 13:28   #14
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Quote:
Originally Posted by science_man_88 View Post
IMO it would come from the fact that as well as going faster the seat-belt allows for quicker application of brakes.
Here is the abstract to the paywalled article:

Risk Compensation or Risk Reduction? Seatbelts, State Laws, and Traffic Fatalities*

David J. Houston and Lilliard E. Richardson
Article first published online: 6 NOV 2007
Quote:
Objective. The risk compensation hypothesis suggests that drivers enjoying greater safety will drive more recklessly and thereby impose greater risks on nonoccupants. We provide a test of the risk compensation hypothesis in the context of state seatbelt laws and belt use rates.

Methods. Fixed-effects models with policy and demographic variables are estimated using annual state data from 1985 to 2002 to test the effect of seatbelt laws and seatbelt use rates on logged fatality rates for occupants, pedestrians, motorcyclists, and all nonoccupants in separate models.

Results. Contrary to the risk compensation hypothesis, the results indicate that both occupants and nonoccupants enjoy greater safety due to state mandatory use laws and increased safety belt use rates.

Conclusion. Overall, seatbelt laws and the higher belt use these laws induce do not increase nonoccupant risk exposure. If anything, these laws and the accompanying increase in belt use result in safer driving behavior.
So the conclusion is that people drive safer with a seatbelt on. Odd, and somewhat contrary to many assertions elsewhere but I'm not paying to take a closer look.
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Old 2014-08-19, 13:47   #15
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It could also come from an irrational human reaction: the seat belts remind the driver that there is danger to their lives, and rather than (logically) compensating for the lowered risk they drive more cautiously because the risk is on their mind. (You'd expect this effect to be greatest shortly after a change, where people unaccustomed to wearing seat belts were suddenly forced to do so.)
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Old 2014-08-19, 14:12   #16
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As a personal note, I have been so long acclimated to wearing a seat belt, that when I have ridden Amtrak I have found myself looking for something to buckle when I take my seat. When driving, I have a hard time moving the car at all without the belts.

One additional point is that in emergency maneuvers the driver is less likely to be thrown around and more likely to retain control.
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Old 2014-08-20, 09:23   #17
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Quote:
Originally Posted by kladner View Post
One additional point is that in emergency maneuvers the driver is less likely to be thrown around and more likely to retain control.
This, I think, was also Scienceman's point, and it seems natural to me too.

Slightly related is the point that usually, in an emergency situation where you have the choice of stopping dead in your tracks or swerving, the former is safer. A driver who isn't wearing a seatbelt may be more inclined to try to steer instead of braking.
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Old 2014-08-20, 09:32   #18
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Quote:
Originally Posted by Brian-E View Post
Slightly related is the point that usually, in an emergency situation where you have the choice of stopping dead in your tracks or swerving, the former is safer. A driver who isn't wearing a seatbelt may be more inclined to try to steer instead of braking.
With ABS you can do both.

I wonder if the above studies considered things like ABS in their figures?
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Old 2014-08-20, 11:33   #19
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Quote:
Originally Posted by retina View Post
With ABS you can do both.

I wonder if the above studies considered things like ABS in their figures?
ABS prevents skidding when braking in a straight line, but it can do nothing about skidding in the direction of original travel due to an attempt to steer sharply at high speed.
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Old 2014-08-20, 15:46   #20
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Quote:
Originally Posted by Brian-E View Post
ABS prevents skidding when braking in a straight line, but it can do nothing about skidding in the direction of original travel due to an attempt to steer sharply at high speed.
For many non-race-experienced drivers ABS allows them the apply the brakes at maximal effort and still retain directional control. For those same drivers without ABS they just end up skidding in a straight line and no amount of steering wheel manipulation will allow them to turn to a different direction. Also skidding reduces deceleration and increases the stopping distance.

ABS is something that has a great benefit because it allows inexperienced and panicky drivers to remain in control of the vehicle for longer than they would otherwise be capable of with manual manipulation of the brake pedal to keep the wheels turning.
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Old 2014-08-20, 16:30   #21
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Quote:
Originally Posted by retina View Post
For many non-race-experienced drivers ABS allows them the apply the brakes at maximal effort and still retain directional control.
[snip]
When the Chicago Police Dept. got its first round of squad cars with ABS, the cops hated them because they could no longer do intentional skid maneuvers.
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Old 2014-08-20, 17:06   #22
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Quote:
Originally Posted by retina View Post
Also skidding reduces deceleration and increases the stopping distance.
Oh. My. God. Finally someone who knows this. There is the occasional person who understands that flooring the gas pedal on a slippery surface doesn't help and that your best bet is "as fast as you can without slipping" and that any additional speed past the initial slip point is meaningless.

However, this is the first instance of someone not needing me to explain that you stop faster when not skidding. Thank you for being (EDIT: extra) intelligent.

Quote:
Originally Posted by kladner View Post
[snip]
When the Chicago Police Dept. got its first round of squad cars with ABS, the cops hated them because they could no longer do intentional skid maneuvers.
I think in most cars this sort of thing can be turned off. ABS in dry conditions can almost be turned off by default. In the winter, intentional skid maneuvers are probably too dangerous anyway.

Last fiddled with by TheMawn on 2014-08-20 at 17:07
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