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Old 04-01-07, 07:40 PM   #1
BobSmalls
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How fast of a car-bike collision can be survived?

Suppose I were travelling at 12mph on a bike when I was rear-ended by a car travelling 40mph. Would that be fatal? What if the car were going 30mph or 50mph?

I'm an engineering student. I live two miles from campus. I own a car. I'll drive it if I have to, but I'd rather be cycling.

The proposed route is one mile along a two-lane road with 40mph traffic and a "bicycle lane" which is basically a wide shoulder with a paralellogram painted on it, then one mile down the same road with the same bike lane after it widens to four lanes and speeds up to 55mph traffic (speed limit 45). I consider the chance of being hit to be slim, but the consequences of such a collision are quite unknown to me.
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Old 04-01-07, 08:07 PM   #2
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1) If it's only two miles each way, have you considered walking or jogging? (At age 56, I cover anywhere from 4 to 9 miles per day on foot, averaging 5 to 6, as part of my commute and general transportation.) A two-mile-each-way commute will destroy your car in no time.

2) Will your commute ever involve riding after dark, into the rising or setting sun, inclement weather, or other hazards? Even in broad daylight, high-visibility clothing will definitely enhance your odds of avoiding a serious collision. At night, good, bright front and rear lights are a must.

3) To return to your original question, speed undeniably kills. Your odds of surviving a collision with a motor vehicle traveling 15 to 20mph are decent, but they drop to almost nil if you are struck with a car going, say, 50mph. (In San Diego County, we just lost a very experienced and talented cyclist when he was struck from behind on a 55mph road in Poway.)
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Old 04-01-07, 08:09 PM   #3
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If you have a wide shoulder (er, bike lane), I wouldn't worry about fatal speed differentials. The odds of an untimely demise om that road are probably very small. However, I can understand your discomfort; I try to avoid roads where the cars are going much faster than 40 mph myself. Are there alternative routes?
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Old 04-01-07, 08:58 PM   #4
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A public service radio spot that I heard on Friday said that a person has an 80% chance of surviving being hit by a car going 20 mph and an 80% chance of dying from being hit at 40 mph. You would have to do some physics to apply that to a moving bike and an opposing car, but if you cared to it would not take long. That statistic sounds like some pretty sketchy science to me and there are a lot a variables, but I offer this as a "data" point in case it helps. Plus, I remembered it, which is rarer and raret these days....

[edit] ... Of course, simply surviving might not be such a great deal if you ended up incapacitated with a diminished quality of life and long term care issues to deal with (um... guess I am a little down today). I guess I would find another route if I were you.

Good luck and BE SAFE OUT THERE!!
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Old 04-01-07, 10:02 PM   #5
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I'm not sure about bicycles, but I've had friends die on motorcycles at under 40 mph, and had other friends walk away from 180+mph (on the track) lay downs.

Sometimes life is unpredictable. The real questions are what you hit, and how you hit it. The speed required to do damage is actually rather low, but the conditions under which those low speeds actually DO do that type of damage are amazingly rare.

-- James
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Old 04-02-07, 12:40 AM   #6
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You can die from tripping and hitting your head. Do you intend to wear a helmet? That may be the big variable.
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Old 04-02-07, 12:46 AM   #7
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The most dangerous thing you do all day, unless you walk a highwire without a net, or are a dud bomb tester, is get in and out of the shower every day.

The perception of rear ending danger on a bike is far higher than it actually turns out to be....(I sound like Helmet Head! ). Wear High Visibility yellow or ANSI Safety green and use a blinkie light and you'll be fine!
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Old 04-02-07, 07:03 AM   #8
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I got hit head on by a car that seemed to be going 15 to 20mph. I was going 25mph. It hurt, but nothing was broken.
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Old 04-02-07, 07:08 AM   #9
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Quote:
Originally Posted by John E

3) To return to your original question, speed undeniably kills. Your odds of surviving a collision with a motor vehicle traveling 15 to 20mph are decent, but they drop to almost nil if you are struck with a car going, say, 50mph. (In San Diego County, we just lost a very experienced and talented cyclist when he was struck from behind on a 55mph road in Poway.)
That said, bear in mind that the wrong head hit, just falling of a bike not even moving, can kill too. A lot really depends on how you are hit. But indeed the higher the vehicle speed, the more energy it will impart into the human it hits.
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Old 04-02-07, 07:25 AM   #10
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My only accident so far has been a door prize while I was riding a MTB at around 20kmh

I flew in a parabolic curve and landed in pushup position without skidding, so I got lucky there... my handlebars were slightly misaligned and a brake cable was severed.

However, the Honda Civic's door was left barely attached to the car.
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Old 04-02-07, 09:07 AM   #11
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Quote:
Originally Posted by BobSmalls
Suppose I were travelling at 12mph on a bike when I was rear-ended by a car travelling 40mph. Would that be fatal?
If I may speak from first hand, personal experience ... ALMOST.

I got run down from behind by an SUV estimated by witnesses to be going 50mph. I lived, but barely.

Multiple broken bones, tire marks on my helmet, 2 days of memory loss (could be from the sedation at the hospital), and became septic and seriously sick from post-crash infections.

Ran down from behind

Post crash pic - the bike

I survived physically, mentally .... ?

However, when recovering from this crash I discovered Bikeforums (wasn't much I could do besides surf the web or watch TV). So something good did come of it.

jw
(no, the driver was never caught)

Last edited by John Wilke; 04-02-07 at 09:20 AM.
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Old 04-02-07, 01:52 PM   #12
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It seems the consensus is consistent with the theory: Each additional MPH is much more dangerous than the previous one. Further, even during the 40mph portion of my commute, being hit by a car would be very serious.

@bragi: This IS the alternate route. The more obvious and shorter route is down a 55mph (45 posted) divided highway with narrow shoulders. Hey, at least there's no cars parked on the street.

To JW and others: I'm glad to hear you're riding again/still.

I know Honda is very interested in safety, especially pedestrian crash safety. I wonder whether they test their doors in door-bike scenarios. Probably not, since you'd survive hitting just about any door. All the better if you sail over it.


I rode today despite the wind. I saw two other cyclists during the fifteen minutes I was out. I haven't heard of any cyclist deaths on local bikepaths or roads, so I'm going to guess it's safe enough.
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Old 04-02-07, 02:08 PM   #13
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You will be safer on the bike than in the car, because you wont be sharing the lane with other cars.
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Old 04-02-07, 03:12 PM   #14
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Quote:
Originally Posted by AndrewP
You will be safer on the bike than in the car, because you wont be sharing the lane with other cars.
I see two things wrong with your comment... many of us do "share the lane" either beside or in front of cars... the latter case putting us right in line for the same rear end collisions that make up the majority of auto crashes.

The other issue is debatable as those statistics never compare cars to bikes with both moving at the same speed. They compare all auto collisions to all bike collisions.

Try comparing auto collisions at or below 30MPH to bike collisions.
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Old 04-03-07, 12:06 AM   #15
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There are other factors besides speed that determines how bad a car vs bike wreck will be. For example, if you got hit from behind, did you go under the car or on top of the hood?

That said, of course the more speed, the more likely you will die.
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Old 04-03-07, 07:43 AM   #16
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Quote:
Originally Posted by genec
I see two things wrong with your comment... many of us do "share the lane" either beside or in front of cars... the latter case putting us right in line for the same rear end collisions that make up the majority of auto crashes.
The situation the OP was describing was riding on a shoulder next to busy traffic lanes. I would rather ride on an expressway service road without a shoulder, than a city street with a lot of intersections/driveways, because there is a much higher chance of being hit by crossing traffic than following traffic.
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Old 04-03-07, 12:01 PM   #17
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That is an impossible thing to quantify. You can't simply attach a speed to it and say it will or will not be fatal.

Where are you taking the impact? Helmet? Face? Spine?
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Old 04-03-07, 12:36 PM   #18
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That is an impossible thing to quantify. You can't simply attach a speed to it and say it will or will not be fatal.

Where are you taking the impact? Helmet? Face? Spine?
Yeah, but if had to chose between two risks ... getting hit at 30 mph, or 50 mph, isn't that choice easy?

I know a lot of folks here preach about 'taking the lane'. Me? I ride as far to the right as possible, a glancing blow is better than a direct hit.

jw
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Old 04-03-07, 01:14 PM   #19
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I was sideswiped on Feb. 18th by an idiot pulling a wide trailer and put on the ground. I was traveling 40 mph, and the guy who hit me was probably going close to 55.

Thankfully, the trailer wheels didn't run over me, I didn't bounce off the trailer, and I took a fairly good fall.

The damage:

My beloved 2001 Trek 5200 (on which I had crossed the Continental Divide in Colorado 10 times, and summited Alpe d'Huez) was totaled.

Every item of clothing I was wearing, except for socks and shoes, were totaled.

I "escaped" with no broken bones, but required about 20 stitches in the knuckles of my right hand, and in my left elbow (which was opened to the bone). Plus a bunch of road rash on left hip and shoulder.

I think I was pretty lucky...some of my friends riding behind me thought I was going to be dead when they got to where I'd gone down.
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Old 04-03-07, 01:16 PM   #20
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Quote:
Originally Posted by John Wilke
Yeah, but if had to chose between two risks ... getting hit at 30 mph, or 50 mph, isn't that choice easy?

I know a lot of folks here preach about 'taking the lane'. Me? I ride as far to the right as possible, a glancing blow is better than a direct hit.

jw
That's a good way to invite getting hit...and, a glancing blow that puts you into a phone pole, or results in your head striking a concrete curb, could be fatal even at low speeds.

Better to use a mirror and be assertive...hugging the right side is just inviting cars to pass when it's not safe.

Edit: sorry...I didn't see your post above about getting hit high speed. I could see how that could change things for you.
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Old 04-03-07, 02:03 PM   #21
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Quote:
Originally Posted by SSP
I was sideswiped on Feb. 18th by an idiot pulling a wide trailer and put on the ground. I was traveling 40 mph, and the guy who hit me was probably going close to 55.

Thankfully, the trailer wheels didn't run over me, I didn't bounce off the trailer, and I took a fairly good fall.
Wow, bad as your injuries were, you were fortunate your injuries weren't worse. Obviously the idiot caused you to fall, but do you think your injuries are mostly if not totally related to hitting the ground at 40 mph without being stopped by an immoveable object like a guard rail or tree. In other words, the motor vehicle caused the fall but its velocity didn't add to the trauma. I suspect your own speed would be irrelevant if your body was struck broadside by a vehicle going 40 mph. Or the motor vehicle speed would be irrelevant (it could even be stopped) if you struck the side of it at 40 mph and were instantly decelerated to 0MPH.
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Old 04-03-07, 02:20 PM   #22
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Quote:
Originally Posted by I-Like-To-Bike
Wow, bad as your injuries were, you were fortunate your injuries weren't worse. Obviously the idiot caused you to fall, but do you think your injuries are mostly if not totally related to hitting the ground at 40 mph without being stopped by an immoveable object like a guard rail or tree. In other words, the motor vehicle caused the fall but its velocity didn't add to the trauma. I suspect your own speed would be irrelevant if your body was struck broadside by a vehicle going 40 mph. Or the motor vehicle speed would be irrelevant (it could even be stopped) if you struck the side of it at 40 mph and were instantly decelerated to 0MPH.
Yes...I was very fortunate it wasn't worse. I had a few days of minor PTSD, but now that I have a new bike, I'm back to my old self mostly (though I've vowed to never again ride without the mirror unless I'm racing).

As for my injuries - I think the speed of the vehicle didn't make much difference in this case. It would have been about the same if it had been a single-vehicle bicycle accident (e.g., a blown front tire at 40 mph). Basically, I just got bumped really hard by the rear wheels of the trailer as he swung back into the lane....the bump was no big deal, but hitting the ground at that speed sure was.

I think I just went down hard to the left and tumbled forward only once...basically, a quick fall and quick deceleration to 0 mph. Full details, plus links to photos for the interested and/or ghoulish, in this thread.
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Old 04-03-07, 08:26 PM   #23
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Quote:
Originally Posted by BobSmalls
Suppose I were travelling at 12mph on a bike when I was rear-ended by a car travelling 40mph. Would that be fatal? What if the car were going 30mph or 50mph?
I speak from first hand experience also. I got run over from behind by an SUV going at least 55 mph. I was doing 15, so about a 35 mph difference. I had no broken bones, just my left arm abraded/blistered from shoulder to wrist by the SUV's right front tire and some lingering nerve damage to two fingers on my left hand. Just a visit to the doctor.

If I had been on one of my bikes, I would agree with jw ... ALMOST
Luckily, I was on my recumbent trike. I was stiff, sore and bruised but, alive and kicking.

To JW: My SUV driver didn't slow or brake until he realized he had a flat tire.

Ron
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Old 04-03-07, 11:30 PM   #24
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Anecdotal evidence for surviveable collision at 30 mph:

I was hit head on recently by someone who was cutting the corner while making a turn (I was just departing from the stop line at the intersection he was turning on to). We both had our vision obscured of eachother because a bus was passing when we made our respective turns, so we were both at fault. He hit me straight on at 30 mph and sent me flying into the air after breaking his windshield. He got out of his car and I overheard him speaking to a 911 operator - "Hello, I just killed someone on a bike." It was surreal. I walked away with a swollen ankle and some road rash.

Each accident is unique, though, and you can't make generalizations; I just wanted to share an interesting experience I had.
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Old 04-04-07, 07:53 AM   #25
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have you seen this video?

frightening yet, somehow, oddly reassuring.

http://www.youtube.com/watch?v=tth9krDtxII
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