BlazingPedals wrote:I'm not arguing for or against speed, but I should point out that your math only allows for hit-from-behind accidents. Only about 1 in 7 are of that type; most are right-hooks, left crosses, or cars coming out of a side street.
Good point! Let's compare:
Biker at 10 mph vs 20 mph in a 30 mph traffic situation.
Per mile - 10 mph biker will be:
1. passed by 4x (times) as many vehicles =
a. 4x the possibility of hit, or swipe x (2x impact speed)
b. 4x the possibility of "right cross" **
2. 2x the volume of oncoming traffic =
a. 2x the possibility of "left cross" **
b. 2x possibility of head on x (.8 impact speed)
(30 + 10 mph vs 30 + 20 mph = 80% impact speed)
3. 2x the volume of cross traffic, sidestreets, driveways etc. =
a. 2x the possibility of cross traffic collision **
Twice as long, being a target, in the intersections!
Note: Actual percentages listed where available. Other impacts are highly variable due to possible angle and bike into vehicle or vehicle into bike. **
Speed, or severity, of impact will vary, from 50% to 100% (possibly higher).
Best case is 50% impact speed of 10 mph biker into side of vehicle.
Worst case would be, side impact of biker by car, 100% impact speed. Possibility of being "run over" might be 2x, for the 10 mph biker. (Momentum of 20 mph biker is much more likely to carry him past the car = much greater chance of not being under car!)***
(Same direction impact already established at 4x possibility & 200% speed-severity.)***
20 mph Biker possibility of impact is approx. 25% to 50% that of the 10 mph Biker.
Additionally, 20 mph Biker is 2x as likely to strike the vehicle while the 10 mph Biker is 2x as likely to be struck by vehicle. (Applicable to all, except same direction & head-on!) Possibility of 10 mph Biker going under vehicle is MUCH greater!
The final, measurable, variable might be, "time to see", (tts), the biker. (10 mph biker) While following traffic only has .5x the tts, oncoming traffic has 1.25x the tts, and the cross traffic has 2x the tts.
The additional factor of faster motion being more noticeable, especially in the peripheral vision area, should be added, but, I'm afraid, assigning percentages would be sheer speculation.
(Peripheral vision is much more attuned to detecting motion, as well as light, especially flashing light. Another good reason for a "strobe" headlight, during the day.)
Personally, I believe, faster still looks a whole lot better-safer.