A Common Misconception

Discussion in 'Electrical' started by loquin, Dec 21, 2009.

  1. loquin

    loquin Active Member

    is that we need lights as powerful as a motorcycle on our bikes at night. It's just not so. More light IS better at a given speed, but, remember that motorcycle lights are designed to provide enough light for the rider to see far enough ahead to stop, at freeway speeds. 70 MPH.

    The issue is that the light energy density varies as the square of the distance. To double the distance that you can see, you need 4 times the lighting; to triple the distance, you need 9 times the lighting.

    However, the distance you need to see ahead is roughly dependent upon the square of the speed that you're traveling (the amount of energy that has to be absorbed by the braking system is proportional to the square of the speed as well.)

    Assuming that we are traveling at 1/2 of freeway speed (35 MPH) we would need 1/4 the distance to stop, all other factors being equal, as the motorcycle, and the lighting requirement for 1/4 the distance is 1/4th of 1/4th, or 1/16th the power of the motorcycle headlamp, if the same amount of light per watt is produced. So, a 50 watt headlamp on a motorcycle at 70 MPH could have a 3+ watt equivalent headlamp on a bicycle, and you would have objects being seen in time to stop.

    Would it be nice to see an object as far away as you could with a motorcycle headlamp? Absolutely! But, it's not needed for safety.
    Last edited: Dec 21, 2009

  2. augidog

    augidog New Member

    interesting, Lou...but day & night riding are two different things, so if you don't mind i'll toss a coupla pennies in here.

    lights are for seeing at nite and for being seen during the day.

    seeing: nothing wrong with overkill if your setup can handle it...if you've ever topped a rise at 30mph and seen those shiny eyes 1/4 mile down the road, you'll be glad you have some candlepower, most deer outweigh you and the bike. but it only takes a minimum amount of light to be safely seen at nite. make your own choice & ride within the limits of your equipment, imo. edit: if there's a chance of roadside pedestrians at nite in your area, please consider something more than a minimal 3w.

    being seen: i think daylight is the time for motorcycle-grade lighting. it's amazing how much room we're given at intersections & such when peeps aren't sure what's coming at 'em and how fast. again, make your own choice, but factor the mindset of the average cager...if they see bicycle-grade lighting, they'll think "slow" and usually pull out in front of you, if they see a "real" headlight they will hesitate in the name of caution, isn't that what safety equipment is all about after all?

    i'm just sharing some opinions based on some experiences is all :)
    Last edited: Dec 21, 2009