Surprise! :) The bar is (literally, not figuratively) set by the crash test regulations in a given market. In the US, this is the NHTSA.
In the incident outlined in the article, the driver struck a pole orientated (roughly) perpendicular to the direction of travel. The testing standard for this type of impact is currently 20 MPH[1]. Why 20 MPH? Because, as you suggested, research [2] indicates that most accidents involving fixed poles don't occur at high speeds. Roadside hardware present on highways are designed to crumple and absorb impact, or are situated such that they would deflect the car, rather than cause it to stop abruptly. Yes, you can find exceptions to this rule, but they are exceptions, and would be considered a deficiency to be resolved, not an engineering standard.
Tesla exceeded the required criteria for this test by a sizable margin, but you've got to look at the physics of kinetic energy to understand why anything above 55 MPH is still wildly outside of the range considered in the safety engineering of the car.
In a crash, the kinetic energy of the vehicle must be dissipated somehow. This energy is governed by the formula (1/2)mv^2. The important part of that formula is the velocity-squared portion. The velocity coefficient impacts the kinetic energy as a square. Just have a look at a graph of that function:
My point was more that if they are doing some design calculation, they aren't just going to plug 55 mph into the front of that calculation, they are going to use some consideration.
Shortly after posting my other reply, I was pondering how worthwhile it was and what prompted me to post it, and I decided that I found the 55 to be overly specific. I haven't changed my mind about that, but I don't see much reason to try to argue about it.
Then how do you plain that the car split in half in this incident? If the information presented doesn't change your mind, then maybe you're just more concerned with maintaining your point of view than you are understanding the matter.
I suppose the key point is that I over-read Interstates are the only environment where an automobile should exceed 55 MPH (if you're obeying traffic laws). (which is simply not true) and looked past there is no testing standard (which does a nice job of qualifying what you were saying).
In the incident outlined in the article, the driver struck a pole orientated (roughly) perpendicular to the direction of travel. The testing standard for this type of impact is currently 20 MPH[1]. Why 20 MPH? Because, as you suggested, research [2] indicates that most accidents involving fixed poles don't occur at high speeds. Roadside hardware present on highways are designed to crumple and absorb impact, or are situated such that they would deflect the car, rather than cause it to stop abruptly. Yes, you can find exceptions to this rule, but they are exceptions, and would be considered a deficiency to be resolved, not an engineering standard.
Tesla exceeded the required criteria for this test by a sizable margin, but you've got to look at the physics of kinetic energy to understand why anything above 55 MPH is still wildly outside of the range considered in the safety engineering of the car.
In a crash, the kinetic energy of the vehicle must be dissipated somehow. This energy is governed by the formula (1/2)mv^2. The important part of that formula is the velocity-squared portion. The velocity coefficient impacts the kinetic energy as a square. Just have a look at a graph of that function:
http://www.wolframalpha.com/input/?i=1%2F2%282100x%5E2%29+fr...
As much as I commend Tesla for their safety efforts, when you drive like this guy did, your only ally is dumb luck.
1: http://www.safercar.gov/Vehicle+Shoppers/5-Star+FAQ#fifteen
2: http://www.nhtsa.gov/CARS/rules/rulings/SideImpact/index.htm...