I would like to ask, what's the difference in blinding another driver with hi-beams and blinding them with a blindfold? Blind is blind. I only flash my high beams when I see a left blinker.That helps the cage see me. On the interstate I run my hi-beam a little more than I should, but never when approaching another cage.
Stolen from a Kawasaki versys forum.
Scientific evidence supporting DRLs, high-beams, hi-viz
Up to this point I haven't seen a review of the scientific literature regarding the various safety implements that we as riders may choose to use: hi-viz, reflective junk, DRLs whether high- or low-beam, and headlight modulators. Having a bit of spare time I though I'd look through the literature to see if there's data behind the paranoia, and it looks as if there is some evidence indeed.
Torrez LI. MOTORCYCLE CONSPICUITY: THE EFFECTS OF AGE AND VEHICULAR DAYTIME RUNNING LIGHTS. PhD dissertation submitted to the University of Central Florida, 2008. (pdf link, click!)
All emphasis in quoted sections below is mine unless explicitly noted. This dissertation, which I just found now thanks to Google Scholar, is a fantastic resource for safety-hounds.
Literature review with regard to daytime use of high-beam headlights, low-beam headlights (DRLs), and headlight modulators:
[The Franklin Institute report] concluded that the use of high beam and low beam headlights dramatically increased the conspicuity of motorcycles, as was evident in their decreased accident involvement (Janoff et al., 1970).
[Williams and Hoffman] found that overall conspicuity was increased when high and low beam headlight conditions were compared to no light conditions in both cluttered and uncluttered environments and that compared to all the other implements tested, the high beam was most effective
(Williams & Hoffman, 1979).
In [the 1981 study by Olson, Halstead-Nussloch, & Sivak] an actual motorcycle was equipped with various implements used to increase conspicuity such as fluorescent garments (discussed later in paper), running lights, high/low beam headlights, and modulating headlights (3 Hz) as well as respective coding devices. The results from this study indicate that during daytime [and nighttime] conditions, both low and high beam headlights as well as modulating headlights significantly improved conspicuity.
Literature review with regard to fluoro and hi-viz gear, including reflectivity and the chevron pattern:
The colors white, crème, and lime yellow have all been found to be more conspicuous than any other color of vehicle in studies evaluating accident involvement (Allen, 1970; Solomon, 1990). The results from these studies are questionable as there is a high degree of validity as to confounding variables such as individual behavioral characteristics and color selection (do safer drivers choose white cars)
In the field of emergency vehicle design, it is extremely important in increase conspicuity as much as possible due to the particular types of situations and traffic these vehicles must navigate. In doing so, a large amount of research has been directed toward patterned vehicle applications, mostly overseas (Tijerina, 2003). One such potentially promising pattern is the Chevron pattern, or Harlequin “Battenburg Livery” as it is called in Europe (See Figure 2). This pattern apparently plays off of human perceptual cues by representing similarity to a horizontal barricade or bridge abutment, and consequently increasing conspicuity when applied to emergency vehicles (CVPI, 2004).
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In a study conducted by (Woltman & Austin, 1973), motorcyclists equipped with fluorescent garments were detected much quicker than those wearing conventional colors under a variety of backgrounds, at a variety of angles. This was especially true under environmental conditions of dust and or dim illumination.
As mentioned earlier in regards to vehicular lighting, Olson, Halstead-Nussloch, & Sivak (1981) additionally tested the effectiveness of fluorescent garments on motorcycle detection and found their use to effectively distinguish the motorcyclist from their surroundings via a gap acceptance paradigm. These findings have been supplemented by support from research on pedestrian and bicyclist conspicuity, where virtually every study done has concluded that both fluorescent and retro-reflective garments drastically improve conspicuity (for an exhaustive review see Kwan & Mapstone, 2004).
Experimental data and conclusions involving age, modulators/no modulators, and motorcycle conspicuity:
The results indicate that there was not a significant difference [in reaction time or distance detection measures] between the headlight modulated condition and the headlight ON condition. This was likely the result of the environmental conditions tested in this study (clear day/rural intersection). Research shows that headlight modulators are most effective when used in inclement weather and congested areas.
This research found that it takes older adults over the age of 65 over 200ms longer to detect a motorcycle than younger adults. This is not only significant statistically, but when evaluated in terms of real world applicability, this equates to approximately 7-10 feet of distance for a motorcycle traveling at a rate of 25MPH (refer to Appendix O). If a motorcycle is traveling at 25MPH and it takes an older adult 200ms longer to respond to a motorcyclist, this poses a greater likelihood of accident for these vehicles since the motorcycle will be approximately 7-10 feet closer to the vehicle. This is especially dangerous when taking into consideration the type of crash typology evaluated, where the driver is situated in a left turn scenario.
The current research did not find any significant increase in motorcycle detection performance for older adults as a result of headlight modulators, but it would be interesting to see if other technologies purported to increase conspicuity had a beneficial effect for this particular group. In future research it would be advantageous to evaluate the effectiveness of rider clothing (fluorescent), motorcycle coloring/reflectivity/patterns, auxiliary headlights and flashing beacons as they relate to the motorcycle conspicuity performance of this higher risk group.
My conclusions/long-form Cliffs Notes:
1. There exists much epidemiological evidence that DRLs and daytime high-beam usage reduces accident rates, but this type of study is confounded by selection bias (ie, people who wear hi-viz are safer than those who wear wife beaters).
2. There also exists experimental and basic science evidence that shows that DRLs, high-beam usage, fluoro/hi-viz, and the chevron pattern are detected quicker and more reliably, especially in marginal conditions.
3. Old people have measurably slower reaction times, and this difference is significant enough to make the difference between turning in front of you vs. hitting the brakes. Unfortunately, headlight modulators do not "fix" this problem of old people.
4. Headlight modulators do not show a benefit above DRLs alone in the dissertation above, but in more urban/congested/poor lighting scenarios they might have a benefit.
You can draw your own conclusions from all the above, but I've already drawn mine as illustrated below: