Enhancing Day And Night Visibility For Cyclists

Transcription

1 Enhancing Day And Night Visibility For Cyclists Being seen can literally save your life! This is, of course, critical for riding at night but it can also make a huge difference during the day especially this time of year when the sun angle is low and the shadows are long. Would you bet your life on your blinkie? A lot of cyclists slap a blinkie on the back of their bike (or body or helmet) and think that they are good to go. Unfortunately, this is rarely the case and leads to a dangerous false sense of security. There is much more that can and should be done to enhance your visibility while riding. By: Steve Lund Special thanks to : Steven Goodridge for excellent background information

2 Night Bicycling Visibility

3 Bicycling at Night Important for commuting/utility cycling 1/4 of all car/bike collisions 1/2 of all bicyclist fatalities Most involve improperly lighted or unlighted bicyclists (They weren t visible!)

4 Car/Bike Collisions at Night Data from

5 Motorist Drive Out & Left Turn (20%) Car headlamps do not illuminate crossing bicyclist s reflectors early enough to prevent collisions

6 Motorist Overtaking (25%) Most overtaking crashes occur on roads posted 40mph or higher CPSC bike reflectors are very dim at long distances DUI or hit and run involved in many collisions with lighted bicyclists X

7 Legal North Carolina Lighting Requirements (2016) Every bicycle shall be equipped with a reflex mirror (reflector) on the rear and BOTH of the following when operated at night on any public street, public vehicular area, or public greenway: A lighted lamp on the front thereof, visible under normal atmospheric conditions from a distance of at least 300 feet in front of such bicycle. A lamp on the rear, exhibiting a red light visible under like conditions from a distance of at least 300 feet to the rear of such bicycle OR the operator must wear clothing or a vest that is bright and visible from a distance of at least 300 feet to the rear of the bicycle.

8 Decision Sight Distance Def: the distance needed for a driver to detect an unexpected or otherwise difficultto-perceive information sources or condition in a roadway environment that may be visually cluttered, recognize the condition or its potential threat, select an appropriate speed and path, and initiate and complete the maneuver safety and efficiently. (page 115, AASHTO)

9 Decision Sight Distance Page 116 of AASHTO s A Policy on Geometric Design of Highways and Streets, 2004

10 Visibility Objective Make yourself look like a rolling Christmas tree!

11 Visibility Strategy Take advantage of the human visual system. Add active illumination (lights). Add passive illumination (reflective elements) on bike and rider.

12 Human Visual System Characteristics Sensitive to contrast (i.e. blinking). Sensitive to motion. Sensitive to size (wide field of view). Persistence (image fades slowly).

13 Active Illumination Effective in all lighting conditions from daylight to darkness. Only illumination that works in daylight. Front & rear lights now required for night use.

14 Types Of Active Illumination Lights To See by. Another Presentation! Lights To Be Seen by. This presentation!

15 Light (& Lens) Source Properties Zero sum game No free lunches! Source provides a given amount of light. Lens system determines the distribution of the light. Wide angle dim beam. Narrow angle bright beam. What is missing?

16 Perceived Intensity Or Brightness There are lies, damn lies, and lumen measurements! The lumen measurement is generated by integrating (adding up) the total light output. Lumens tells you nothing about how the light is distributed (beam pattern)! Because beam patterns (optics) varies between lights it makes it nearly impossible to compare lights or even absolute performance based on lumen measurements alone!

17 Serfas Thunderbolt Photos courtesy Serfas, wetestlights.com

18 Light & Motion Urban 500 Photos courtesy Light & Motion, wetestlights.com

19 Good Lights Have Sufficient brightness and viewing angle to be seen at distance. Mount that allows precise aiming. Mechanical stability to stay put during normal usage over road hazards. Adequate run time. Waterproof.

20 Light Installation Aiming is Critical! Best lights have bright narrow beams. Mechanical stability is Critical! Light must not move due to curbs, bumps, railroad tracks, etc. Aim should be horizontal. Use a yardstick, 25-50ft level surface, and a projection wall to set/check aim.

21 Correct Installation? Photos courtesy: Anonymous cyclists!

22 Verifying Your Installation Stationary on-street, playground, shopping center, etc. Can be done alone. Riding on road course. Requires helper in car.

23 Stationary Verification Find a straight, level road or large parking lot. Lean bike up against a mailbox, signpost or other object. Walk back 500 feet to check aim. Walking side-to-side at distance can check horizontal aim. Vertical aim can be checked by walking towards the light and looking for a sudden increase in brightness.

24 On-road Verification Pick a short, rural road loop with some straight-aways. Motorist helper to observe rider. Extra points if driver age 50+, wears glasses. Rider gets several minute head start. Motorist encounters cyclist in random locations and at posted speed limit. Repeat as needed. Car or cyclist reverses direction to check front light(s).

25 Passive Illumination Requires retro reflective devices or materials. Requires bright supplementary illumination (i.e. car headlights) to work. Pretty ineffective during the day. Can be added cheaply and easily and is always there.

26 Problems With Reflectors Must NEVER be used as the sole method for guaranteeing your visibility! Here is why

27 Lights vs. Reflectors Experiment Under automobile headlamps at various ranges: (a) Planet Bike Superflash LED Light (b) Bargain LED Light (c) Auto Reflector (d) Bike Reflector (a) (b) (c) (d) 50 Feet 100 Feet 200 Feet 400 Feet 600 Feet

28 Physics: Bike Lamp Power Range = R Light reaching motorist decreases 1/R 2

29 Physics: Reflected Light Power Range = R Light reaching reflector decreases 1/R 2 Small reflector intercepts tiny % of lamp output Reflector disperses intercepted light 1/R 2 So observed light power decreases 1/R 4

30 Other Limitations of Reflectors Car headlights may not be on Curves/hill crests affect beam orientation

31 Retro Reflective Advantages Can take advantage of human visual system. Size. Motion. Helps define that you are a cyclist and the direction you are moving. Always ON if mounted on bike. Weighs very little.

32 Retroflective Material 3M Scotchlite type 580 material. Available on: Ebay, Amazon. Advance Auto used to carry it in stores but now only online.

33 Places For Reflective Material Wheels Frame Racks Crank Arms Pedals Shoes

34 The End Result! Shorter Range Longer Range

35 Reflective Accessories Photos courtesy Nathan Sports

36 Play The Odds In Your Favor! Avoid riding at low contrast times dawn & dusk. Avoid riding directly into sunrise or sunset. Choose routes to avoid heavily traveled roads Try Google Maps or Choose ride times to avoid heavy traffic if possible.

37 Final Thoughts You have the ultimate responsibility for your visibility. Don t take shortcuts! Help spread the word.

38 See Also Light & Motion's bicycle light testing web site. 3M 580 reflective material pdf Automotive/Aftermarket/Products/~/3M-Scotchlite-Reflective-Tape in-x-36-in?N= &rt=d Automotive/Aftermarket/Products/~/3M-Scotchlite-Reflective-Tape in-x-36-in?N= &rt=d

39 See Also Recent Bike Light Reviews On MTBR ANSI FL-1 Flashlight Standard Links Understanding-ANSI-FL1-Standard.pdf %20PELICAN%20-%20Explanation.pdf