i tried to fly out today and i ended up being bent

[redacted]

Interesting. I have followed this thread from the beginning but never checked the numbers. Even if he was out of the water by 11:30am, that'd be 20 hours - well within DAN's guidelines but. It'd be difficult to do 2 wreck dives and be out of the water by 9:30am to fit the story huh?

Once you turn a commercial jet and require it to make an unscheduled landing, I imagine you will need a good one.

 

[sdiver68]

I understand your motivation and to some extent it is good, but also has some drawbacks. Here is an analogy:

You can increase your safety on the road by driving 5MPH under the speed limit. It will in fact do that.
However, the arbitrary 5mph buffer may not be enough in some conditions (snow & ice) or totally useless in others.
In our case (the yellow zone) we don't even know the magnitude of the buffer (is it 1mph, 10mph, 20mph?)

Bottom lines is you constantly need to asses the big picture including all risk factors before planning every dive.

Your analogy does not hold true. The safest speed is 8 mph faster then the average speed if traffic. Speed alone is not unsafe.

 

[vladimir]

Your analogy does not hold true. The safest speed is 8 mph faster then the average speed if traffic.

I'd be interested in seeing the source of this. Though it is consistent with my personal experience, 8 mph seems like an arbitrary value. It's the same whether traffic is going 35 mph or 65 mph? That doesn't seem right. I just read this article in Slate last week, which makes a different claim:

The concept plays, in part, on one of traffic engineering’s core truths: Big speed differentials are dangerous. This is laid out in the “Green Book,” the bible of the American Association of Surface Highway Transportation Officials. “Crashes are not related as much to speed as to the range in speeds from the highest to lowest,” the book states. “Studies show that, regardless of the average speed on the highway, the more a vehicle deviates from the average speed, the greater its chances of becoming involved in a crash.”

 

[DandyDon]

Maybe so, but the faster car will hit harder. :shocked2: I really doubt that 8 mph over average is safer will hold up in a traffic stop or court.

I generally dive 60 in a 70 just to save 20% on gas, in the slow lane thank you. No one wants to encounter a car doing 35 in a 70, but now that some hiways are going to 80...?

 

[Tortuga68]

 

[sdiver68]

For those interested, read up on the 85th percentile rule for setting speed limits and the Solomon curve. I don't want to post links on these topics since there are thousands on Google. In many ways you are right, it's not speed that kills rather speed variance.

However, the 8mph I referred to was from 1 of those studies and was for typical interstate highway travel with a 65mph speed limit. It holds up when looking at a speed plotted Solomon curve in comparison to the 50th percentile speed. The theory behind that particular conclusion was for a rider to only have 1 threat zone to worry about, that being those vehicles in front of the rider. If I find that direct link I'll publish it here.

And yes Don, believe it or don't I've heard and read about that holding up in court...but I wouldn't try it. So the thread does not diverge further this is my last post on this subject, however I think it's very pertinent to challenge commonly accepted safety beliefs that don't hold up to analysis.

 

[GrumpyOldGuy]

Your analogy does not hold true. The safest speed is 8 mph faster then the average speed if traffic. Speed alone is not unsafe.

Neither does the underlined statement.

The Solomon study looked at a subset (fatal accidents) of a subset (multi-vehicle accidents, which < 50% of the total) of a subset (accidents on interstate highways, which are also a relatively small slice of the pie). Its interesting for sure. You might conclude that there is a benefit in being able to spot distracted idiots ahead of you rather than letting them sneak up behind you. It however does not make a board conclusion that driving faster is safer.

Back to diving: We are responsible for ourselves. Its more like driving on an empty country road where there is little threat from other drivers or radar wielding cops. We can drive as fast as we want and need to decide how hard to push it. My original point was we have to decide on the safety margin depending on the conditions. In bad conditions, that margin needs to be a lot bigger than in good conditions. A fixed safety margin (-5MPH in my example or +8MPH in your) are both stupid unless you look at the specific conditions.

 

[GrumpyOldGuy]

View attachment 106288

Sorry officer, I was only going 8 degree off course because a its been scientifically proven to be more fun

How about you write a warning to a nice old guy like me instead of an official scuba police ticket?

Seriously, after 200 post do you really think we have to keep on-topic?

 

[daniel1948]

Speed differential may be relevant to the likelihood of a crash, but kinetic energy is more relevant to the seriousness of a crash. When you do have a crash, your chances of being seriously injured or killed rise in proportion to the square of the speed, which is to say in proportion to the kinetic energy of the vehicles. Cops who have to scrape body parts off the highway will attest to this.

It also becomes more difficult to control a car the faster it goes, as any variation in direction will take you out of your lane in less time at higher speed, and as aerodynamic forces on the car increase exponentially with velocity. I do think that driving with the flow of traffic reduces the likelihood of a crash, but if that flow is too fast, the benefit is lost, and I'll let the flow pass me and join a slower bunch of cars, and go with their flow.

 

[sdiver68]

Speed differential may be relevant to the likelihood of a crash, but kinetic energy is more relevant to the seriousness of a crash. When you do have a crash, your chances of being seriously injured or killed rise in proportion to the square of the speed, which is to say in proportion to the kinetic energy of the vehicles. Cops who have to scrape body parts off the highway will attest to this.

It also becomes more difficult to control a car the faster it goes, as any variation in direction will take you out of your lane in less time at higher speed, and as aerodynamic forces on the car increase exponentially with velocity. I do think that driving with the flow of traffic reduces the likelihood of a crash, but if that flow is too fast, the benefit is lost, and I'll let the flow pass me and join a slower bunch of cars, and go with their flow.

2008 German Autobahn (no speed limit for most cars) deaths per billion vehicle kilometers = 2.2
2008 United States Interstates, same statistic = 4.5

http://www.internationaltransportforum.org/

Sorry I broke my promise but others apparently want to discuss. Now what is it you were saying?