Bike Forums - Number one reason to stop at a stop sign.

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It's not just a matter of kinetic energy - another factor is that the entire kinetic energy of the cyclist is going into the collision, whereas most of the car's kinetic energy will (hopefully) be dissipated by its brakes.

Quote:

Originally Posted by EKW in DC (Post 11572652)

Bottom line, I think Idaho stops are OK, but we should remember that other vehicles already at the intersection have right of way and that we should be vigilant for inattentive drivers since we don't have tons of steel wrapped around us. Best case scenario we're riding on top of 7-8 pounds of steel plus components.

Exactly ... and it sounds like this has more to do with staying aware of your situation, than anything else.

The impact damage is different from Kinetic energy.
F = mv/t

So bicycle can't do that much damage to the car.

If you want to play, pay. Everybody should observe traffic rules.

This ******bag really gave us cyclist a black stain. Thanks Mr. Mayor for solidifying the perception of us by motorists!

http://www.theprovince.com/business/...537/story.html

Quote:

Originally Posted by mikeshoup (Post 11572687)

What if I don't stop, slow down to say, 5-ish mph, can see far enough down the road that no vehicles are approaching and go? Without ever reducing my speed to 0 mph?

And of course, if I do see vehicles approaching, I slow down and stop if that's what it takes to wait for the approaching vehicles to clear?

This is what I do. I think it is very reasonable. The spirit of the law is to ensure that the intersection is observed and that people take turns crossing the intersection if there is more than one person stopping.

Quote:

Originally Posted by mikeshoup (Post 11575975)

F = ma. They would both carry the same force if they're at a constant velocity. (That's zero newtons)

Kinetic Energy otoh, is a 100kg cyclist travelling 50mph carries a substantial more amount of kinetic energy than a 1500kg car travelling 5mph.

KE = 0.5mv^2

KE bike = 0.5*100kg*(50mi/hr)^2 = 125000 kg*(mi/hr)^2 (which is the strangest unit for energy ever, but valid none the less)
KE car = 0.5*1500kg*(5mi/hr)^2 = 18750 kg*(mi/hr)^2

KE bike / KE car = 6.67.

The bike carries 6.67 times more kinetic energy than the car.

Its okay, high school physics was a long time ago for me as well.

While the bike would have most of the energy, the force of the collision will be the same on both the cyclist and the car (Newton's third law), and you could get a (really) rough estimate by doing the change in the rider's momentum over the very small time period. The difference is that the driver is protected by a ****-ton of metal, and the rider is, at most, protected by an inch of styrofoam on his or her head.

Quote:

Originally Posted by rex_kramer (Post 11575821)

I figure if I stop, that's one more thing I'm doing right that no one can complain about.

+1
I'm with you on this one. Most of the time on my commute in the morning I'll 'touch toe' at a stop sign. I do come to a complete stop but it's really only for a second (if that). I do it mainly because of the lurking police hidden in shadows watching. I'm about it as far as traffic at 4:30am...except for the police.

And yes...they do complain. I hear it every day.

Jerry H

the fact that cagers routinely drive like morons is all the more reason to NOT stop at a stop sign.

if you stop and drop a foot, you are susceptible to being steamrolled from behind. also, and more importantly, the longer you are in the intersection, the longer you are at risk. there is also the fact that it may take a few seconds to get clipped back in and your attention will be diverted at this time.

most intersections have good enough site lines that you can roll them at 5-10 mph and still have ample time to stop if you realize someone else has the right of way or may blow through without stopping and crush you.

joeybrooks gives a better explanation of why blowing through stop signs/lights is safer than stopping. i highly recommend his videos to anyone that has to deal with traffic on a bike.