Speed Kills? Maybe Not...

[nimbus]

The dramatic shift away from fatal accidents is much less than 55 miles per hour. For some reason, I think it's in the low 40's. If you get flipped or hit a concrete embankment, the difference between 55, 65 or 75 is negligible. Lower speed would only reduce the number of pieces they have to pick-up off the interstate.

no, lower speed makes a big difference in your reaction time and how well you are able to control your vehicle

 

[mrplunkey]

no, lower speed makes a big difference in your reaction time and how well you are able to control your vehicle

1) What percentage of accidents are dictated by the reaction time of the driver? If someone is texting at 55 mph and hits someone, how does traveling at 65 mph change that?

Here's a quote from the report:

Distraction and not paying attention to the road accounted for 41 percent of the errors. Ten percent of errors were attributed to drivers lacking proper driving skills and either freezing up or overcompensating behind the wheel. Eight percent were asleep, having a heart attack or otherwise incapacitated.

So there's 59% of all accidents accounted for.

2) Given that a wreck is underway, the physics of a body being decelerated dramatically from 55 mph are just as devastating as the physics of being decelerated from 75 mph.

3) Considering that some wrecks are head-on (or at least the primary directions of motion are opposite), you have to add those speeds anyway. So two 35mph drivers that hit head-on are the same as hitting a stationary object at 70 mph.

 

[nimbus]

1) What percentage of accidents are dictated by the reaction time of the driver? If someone is texting at 55 mph and hits someone, how does traveling at 65 mph change that?

Here's a quote from the report:



So there's 59% of all accidents accounted for.

2) Given that a wreck is underway, the physics of a body being decelerated dramatically from 55 mph are just as devastating as the physics of being decelerated from 75 mph.

3) Considering that some wrecks are head-on (or at least the primary directions of motion are opposite), you have to add those speeds anyway. So two 35mph drivers that hit head-on are the same as hitting a stationary object at 70 mph.

dude i never even brought up the physics of a collision. go back to your texting example. somebody going 85 and glancing back and forth between their phone and the road is way more of a threat than someone doing the same thing at 55, because you cover a significantly greater distance during your distracted phase when speeding - meaning there is that much more opportunity for things to go wrong when you aren't paying attention. And when something goes go wrong, like traffic suddently being stopped, it will take you more time (i believe exponentially) to slow down. i mean even go back to your head on collision example: if you are going 60 and someone crosses over the yellow at you head on, you have way less time to react than if you were going 35. Not to mention swerving is much safer at 35 than 60 in terms of maintaining control of your vehicle.

 

[mrplunkey]

dude i never even brought up the physics of a collision. go back to your texting example. somebody going 85 and glancing back and forth between their phone and the road is way more of a threat than someone doing the same thing at 55, because you cover a significantly greater distance during your distracted phase when speeding - meaning there is that much more opportunity for things to go wrong when you aren't paying attention. And when something goes go wrong, like traffic suddently being stopped, it will take you more time (i believe exponentially) to slow down. i mean even go back to your head on collision example: if you are going 60 and someone crosses over the yellow at you head on, you have way less time to react than if you were going 35. Not to mention swerving is much safer at 35 than 60 in terms of maintaining control of your vehicle.

Are you saying someone driving 75 may wreck while someone driving 55 may not wreck and that net reaction time is a factor in that many wrecks? I've never seen a statistic on near-miss wrecks. So how would you even measure that?

And who's to say the driver doing 75 mph isn't driving more intensely due to their speed and the 55 mph driver is less engaged in driving and doing something else? When I'm in a hurry, I speed. When I'm not in a hurry I make phone calls, text people, check email and otherwise screw around.

 

[nimbus]

Are you saying someone driving 75 may wreck while someone driving 55 may not wreck and that net reaction time is a factor in that many wrecks? I've never seen a statistic on near-miss wrecks. So how would you even measure that?

well one thing you can do is plot the percentage of fatal crashes along with the mph past speed limit of the driver. then you can also plot the percentage of miles traveled along with mph past speed limit of the driver. I have some stuff on my other comp i can post tomorrow. But % of fatal crashes either increases slightly or stays the same with mph over speed limit up to i think 20 mph over. At the same time, % of miles traveled by vehicle decreases exponentially with mph past speed limit. In other words, vehicles traveling say 15 mph over the limit account for a much smaller % of traffic than those traveling 5 mph over, but are involved in the same number of fatal crashes, or maybe a little more. Therefore i think you can conclude that risk of being in a fatal crash increases a lot as your speed increases beyond the speed limit.

 

[mrplunkey]

well one thing you can do is plot the percentage of fatal crashes along with the mph past speed limit of the driver. then you can also plot the percentage of miles traveled along with mph past speed limit of the driver. I have some stuff on my other comp i can post tomorrow. But % of fatal crashes either increases slightly or stays the same with mph over speed limit up to i think 20 mph over. At the same time, % of miles traveled by vehicle decreases exponentially with mph past speed limit. In other words, vehicles traveling say 15 mph over the limit account for a much smaller % of traffic than those traveling 5 mph over, but are involved in the same number of fatal crashes, or maybe a little more. Therefore i think you can conclude that risk of being in a fatal crash increases a lot as your speed increases beyond the speed limit.

I saw a curve of estimated speed involved in a wreck versus fatality rate about two years ago and it looked sigmoid-shaped. It was linear, but relatively flat up to 30ish mph. Then it was linear but shifted upward dramatically for 10-20 mph. Then around 50 or so, it flattened out again with slow linear growth upward.

 

[nimbus]

I saw a curve of estimated speed involved in a wreck versus fatality rate about two years ago and it looked sigmoid-shaped. It was linear, but relatively flat up to 30ish mph. Then it was linear but shifted upward dramatically for 10-20 mph. Then around 50 or so, it flattened out again with slow linear growth upward.

ok this is what i have. i guess it's only relevant to city driving; forgot that it was in km/h and not mph LOL. So i don't really know anything about highway speeding; we could probly get away with a higher limit. But i think they are important for city roads. However i still think that it is dangerous for people to be going 80+ given how abruptly traffic can slow, and also how risky an adjust becomes after trying to merge into an occupied lane