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Old 02-14-2010, 12:25 PM   #1
DrkAngel
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Bicycle Safety - The Math of Speed.

Faster is Safer!
My Sister-in-Law just can't understand, why I feel that going faster, on a bicycle, is safer. "30 mph!" ... "You're gonna kill your self!". ...

I feel it necessary to prove that faster is safer. Let me try a mathematical approach.

First, let me qualify;
1. My riding is in an urban area and 95% of the streets-roads are 30 mph limit.
2. I ride on the right side of the road, going "with traffic", as is the legal method.

For ease of math - Let's figure a 10 mile trip, w/traffic @ 10 cars per minute.

At 10 mph -
60min x 10cars - 1/3 (for 1/3 speed of cars) = 400 cars passing you at 20mph.

At 20 mph -
30min x 10cars - 2/3 (for 2/3 speed of cars) = 100 cars passing you at 10mph.
AND, cars have twice the time to notice, and avoid, you!

At 30 mph -
20min x 10cars - 3/3 (for 3/3 speed of cars) = 0 cars passing you!

(Math is simplified - but "sound")

If you concede that most urban bike accidents are directly related to passing cars, then 20 mph would be (4 times safer than 10 mph) x (twice the time the, approaching, driver has to see biker) = 8 times safer @ 20 mph, compared to 10 mph!

A__hole factor! Everyone might agree that, possibly, 1 in 100 motorists are AHs toward bicyclists, (Conservative Estimate!), Going 10 mph you'll get passed by 4, only 1 @ 20 mph and at 30 mph you might never encounter 1.


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Old 02-14-2010, 03:47 PM   #2
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What about

The AHs that are coming at you. Using math you have:

An impact of net 40 mph when riding at 10 mph (Your 10 plus the AHs 30 mph)
An impact of net 50 mph at 20
and an impact of net 60 mph at 30



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Old 02-14-2010, 06:36 PM   #3
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You are correct in theory. The The Solomon curve backs up your assertion.


In reality, in the absence of cops or speed cameras, no one drives the speed limit. In a 30 mph zone,expect motorists to be driving 40 mph or more.

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Old 02-14-2010, 08:43 PM   #4
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Let's face it, if you can maintain 30mph average speed you are not only a better man than I but you are immortal and can't be killed. :P

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Old 02-14-2010, 10:04 PM   #5
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Quote:
Originally Posted by Barmy View Post
The AHs that are coming at you. Using math you have:

An impact of net 40 mph when riding at 10 mph (Your 10 plus the AHs 30 mph)
An impact of net 50 mph at 20
and an impact of net 60 mph at 30

No no no you have it backwards. They are traveling the same direction. So the net vehicle/bike impact speed is equal to the speed of the car - the speed of the bike. So bike going 10 mph and car going 30 impact speed is 20 mph. Bike going 20, car going 30 impact speed is 10. The issue here is that you on the bike should have swerved and went around the car.

Now the bad part is that if the car speed is above the bike speed then the vehicle/bike impact speed starts going up. If the bike is going 30 and car is going 50 then you are back into the 20mph impact speed but now you have the issue of 20 mph vehicle/bike net impact speed and the sudden bike acceleration issue then the bike road impact speed which will be close to initial vehicle impact speed . So if you are on a bike going 30 and get hit by a vehicle going 50 the vehicle impact is 20 mph and the ground impact is 50. So it will hurt just a little bit.

Now it may sound like a good deal but in truth the following is the worst possible scenario. Bike is going 30 mph car is going in the same direction at 30 mph. They hit each other. It sounds like it is a good deal but it is not. Such an accident will rip the space time continuum. The bike and vehicle will meld into a weird conglomeration of carbon fiber and hydroformed steel. Behind them a large black hole will form and start the implosion of the entire universe. Now if the conglomeration vehicle maintains a constant speed that is equal to the speed of the accident then the universe's implosion will occur at a time equal to actual time of the current universe's doom. If they slow down then the time for destruction will be in proportion to the loss of speed. Slower they go the faster the universe implodes. The only hope is for an increase in speed. Such an increase will lead time to reverse. The reversal will back time up to the point of the meld and the 1 will again be 2 and the wreck can be avoided to save the universe. So remember if it ever happens to you Stand up and crank up the speed.

At least I think how all that stuff works.
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Old 02-15-2010, 12:45 AM   #6
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Quote:
Originally Posted by Nigal View Post
Let's face it, if you can maintain 30mph average speed you are not only a better man than I but you are immortal and can't be killed. :P
I'm an out of shape 51 year old, with a poor heart. I got a cheap Ezip Mountain Trailz 2 years ago, electric assist bike, and have been tweaking it into an awesome road machine.

Stock: .................................... Modified

24v Sealed Lead Acid Batteries ... 37v Li-ion batteries (50% speed increase)
450w motor @ 24v ................... 675w motor @ 37v
20T motor side freewheel .......... 16T motor side freewheel (25% speed increase)
7spd 14-28T gear freewheel ...... 7spd 11-32T gear freewheel (32% pedal speed increase)
16-17mph top speed. ............... 30mph capable w/ pedal assist!

Motor alone "bogs" near 27mph, pedal assist appreciated!
Some assist through 32mph.

Check my postings under : http://www.twospoke.com/forum/f41/


EZip Engineering 101
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Old 02-15-2010, 12:58 AM   #7
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Accident :<(...

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Old 02-15-2010, 12:59 AM   #8
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OOPs!

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Old 02-15-2010, 02:07 PM   #9
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Quote:
Originally Posted by Barmy View Post
The AHs that are coming at you. Using math you have:

An impact of net 40 mph when riding at 10 mph (Your 10 plus the AHs 30 mph)
An impact of net 50 mph at 20
and an impact of net 60 mph at 30
Unless you are riding on the wrong side of the road, I can't imagine how this could happen. The odds on a driver being a big enough AH to cross the oncoming lane and "hunt you down" might be 1 in 100 million, if you're "Black" maybe, 1 in 10 million, if you just dumped a "Lover" maybe, 1 in a thousand.

Oh! If you are riding against traffic, then you might have a valid concern. This is illegal and very unsafe! The greater your speed, the more damaging the impact and the less time the driver has to notice you.

Pedestrians are required to walk against traffic but bicyclists are required to ride in the same direction as traffic. good rear view mirror is highly recommended!

EZip Engineering 101
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Old 02-15-2010, 02:54 PM   #10
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What about

the driver who is sleepy and nods off... or one who has to much to drink... or in my case misjudges your speed and cuts a left hand turn in front of you....I woke up in the hospital and spent a couple of days in the "head injury ward"



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