Results 1 to 22 of 22
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    375

    How do I break the "glass" speed barrier?

    After about 6000 miles, I've realized that my speed is not limited by how fast I can pedal my bike, but rather how fast motorists think I'm going, which is something like 10 MPH I think.

    On some parts of my commute, I can get my bike well over 20 MPH on a 25 MPH street, but even if I don't have a stop sign, cars will proceed through their stop sign or make a turn about 50 ft in front of me. From about 25 MPH, it probably takes me close to 100 ft to stop the bike if my math is correct so that is a big problem.

    Lights, steady, flashing, or both do not seem to help.

  2. #2
    mtbr member
    Reputation:
    Join Date
    Apr 2012
    Posts
    1,570
    People expect bikes to screw along at walking speed, and don't consider them actual vehicles. Sad fact of life. and there's not much you can do about it.

  3. #3
    mtbr member
    Reputation: mtbxplorer's Avatar
    Join Date
    Dec 2009
    Posts
    5,168
    You may already be doing this, just without the desired results, but I would try as much as possible to "be the traffic" - consider taking the lane when you're going that fast, as it will both make you more visible from sidestreets/driveways, and perhaps send the driver a signal that you are a vehicle and they need to yield. I'm also a fan of the obnoxiously loud jacket, helmet, etc. That said, I have certain intersections where I know the drivers are habituated to merely slowing before entering the street (despite stop signs) and are more likely to cut me off. How fast are people typically going in the 25?

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    375
    I can keep up with the cars in that stretch of 25 MPH zone since it's about 3% downhill. I don't know the actual speed of the cars though because I don't have a computer.

    I take the lane but leave about 100 ft in front of me because I need that space to safely stop. I can see cars at the intersection make a full stop and wait for the cars in front of me but after the car in front of me passes, they go as if I'm not there.

  5. #5
    mtbr member
    Reputation: BrianMc's Avatar
    Join Date
    Jan 2010
    Posts
    3,414
    Yes. I have had some of the "boy you move fast" at maybe 20 mph. Taking the lane helps. Twenty watts of flashing headlights angled to be seen by cross traffic helps. I move into the right turn lanes off the shoulder as I am definitely invisible on the shoulder. My narrow angle flashing helmet light helps some when I look at them. The what is that response slows them enough. Strange this isn't an issue at night. I think the lights look so UFO-ish that they wait to see.

    BrianMc

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    375
    Quote Originally Posted by BrianMc View Post
    Strange this isn't an issue at night.
    BrianMc
    I didn't think about it until you mentioned it, but I only have this problem during daylight, now that it's not dark at 5pm anymore.

    And mostly in Golden Gate Park, of all places.

  7. #7
    weirdo
    Reputation: rodar y rodar's Avatar
    Join Date
    Jul 2006
    Posts
    5,679
    Quote Originally Posted by jseko View Post
    I can see cars at the intersection make a full stop and wait for the cars in front of me but after the car in front of me passes, they go as if I'm not there.

    I can`t help much JS, but I do feel for you. MtbX`s suggestion to take the lane sounded good, but you say you`re already doing it. B Mc`s uberlighting scheme might work if you`re willing to deal with buying, maintaining, and anti-theftin the extra gear. The only other thing I can think of is to kit yourself up like the stereotypical "arrogant roadie prick" in order to get away from the impresion that you`re toodling along at walking pace. I don`t know how well that would play where you are in the aftermath of the Bucchere thing, though. Maybe they`d try gunning you down! Not to hijack, but has that made any impact on cyclist/non-cyclist relations that you can see?
    Recalculating....

  8. #8
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    375
    Not to my knowledge, but my commute doesn't take me through the areas of SF with heavy bicycle traffic. Within SF, I think most motorists are fairly tolerant especially if the number of bicyclists are higher on a given street. On my commute, I only see one other bicyclist on a regular basis but I don't know where he's going. Only thing I really know is he rides a newish Jamis road bike in a cowboy hat.

    That Bucchere case weirds me out because of the amount of attention it receives yet over 30k people die annually in motor vehicle incidents. About a month ago a 17 y/o was killed on her birthday by a speeding drunk about a mile from where I live yet that barely made blipped in the local news.

    Out of towners are a different story. Park in the bike lane and think nothing of it.

    I have a feel of which streets to avoid even if they are residential streets because they are heavily utilized by automobile commuters which means increased volume of cars and aggressiveness.

    Still though, there was a lot of anti-bicyclist sentiment here in SF area even before the whole Bucchere case, but I felt that tended to be more of the suburbanites working in SF that are not bicycle people. E.g. my boss thinks I'm superman because I ride 4 miles to work. Another colleague thinks his $150 full suspension Walgoose is totally awesome and doesn't understand why I spent $1k on my commute bike.

  9. #9
    mtbr member
    Reputation: BrianMc's Avatar
    Join Date
    Jan 2010
    Posts
    3,414
    I wonder if the 'night thing' is a function of drivers searching for moving lights amongst the visual clutter, so they see us. In the day, they are overwhelmed by too much info and filter the irrelevant out. Unless they think about bikes and motorcycles they don't see us. So they fail to see the gorilla on the unicycle, the elephant on the Harley, or the cyclist. I think there is some threshold of unusualness that we need to cross that upsets that visual filter. Yesterday I had 2 (yes 2!) drivers stop and wait for me to go by when they could have proceeded quite safely. That suggests I should be eating into the 20%-30% that don't see me significantly (see Mtbxplorer's recent thread). In both cases, I used what once was marked as a right turn only lane (no longer so marked) getting out into their scanning zone as I always have. Maybe with the wind behind me and nearly 25 mph, I was clearly not doing 10 mph or less and so made them wary. It was bright overcast and the sun lit the Glo tape on the rims quite well, so maybe I mesmerized them with my visibility awesomeness. I was still on the brake hoods.

    Another point in your original post. If you can get your butt over and behind the saddle to drop the CG for max braking (and avoid the OTB), I wonder how short a maximum braking effort would be from 25 mph. I don't see that speed that often anymore and have not experimented. I was 40 feet from the Chrysler and knew that was not enough room even with the butt back and a saddle in the groin on impact is not a good option, so waited until I was 20 feet away before braking hard so I did not end up under the rear wheels.

    BrianMc

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    375
    I should note that I am only estimating the 100ft figure. I obtained the value of -4.8 m/s^2 for max acceleration for a bicycle on flat, smooth, dry, clean pavement from a document used for developing bicycle facilities. From that

    Guide for the Development of Bicycle Facilities, PDF file: https://bookstore.transportation.org...x?id=1180&DB=3

  11. #11
    jrm
    jrm is offline
    mtbr member
    Reputation: jrm's Avatar
    Join Date
    Jan 2004
    Posts
    9,998
    Some parts of my commute im going as fast if not faster then traffic. I usually take the lane especially if theres parking. My biggest gripe is that most drivers underestimate my speed and full out in front of me or stop right in front of me.
    Wreck the malls with cows on Harleys

  12. #12
    mtbr member
    Reputation:
    Join Date
    May 2006
    Posts
    10,969
    Quote Originally Posted by jseko View Post
    I should note that I am only estimating the 100ft figure. I obtained the value of -4.8 m/s^2 for max acceleration for a bicycle on flat, smooth, dry, clean pavement from a document used for developing bicycle facilities. From that

    Guide for the Development of Bicycle Facilities, PDF file: https://bookstore.transportation.org...x?id=1180&DB=3
    Why don't you just practice some emergency stops and measure the distance....also develop your eyeball to understand the distances....

  13. #13
    conjoinicorned
    Reputation: ferday's Avatar
    Join Date
    Jan 2004
    Posts
    3,530
    Quote Originally Posted by jseko View Post
    I should note that I am only estimating the 100ft figure. I obtained the value of -4.8 m/s^2 for max acceleration for a bicycle on flat, smooth, dry, clean pavement from a document used for developing bicycle facilities. From that

    Guide for the Development of Bicycle Facilities, PDF file: https://bookstore.transportation.org...x?id=1180&DB=3
    all science aside, i really think that 100 ft. is extremely excessive. even at 25mph, i'm not sure it would take 25ft to full stop if i locked both wheels, i've certainly never done a 100ft skid even on dirt or gravel (try this link and play Science of Cycling: Steering + Activity | Exploratorium)

    as far as having the drivers respond more appropriately...well good luck with that, i'm not sure i have a belief that it will ever be possible to truly share the road safely...lights or horns notwithstanding. some motorists just need some more education, but most could care less and a few are actively trying to be dangerous because they hate bikes on the road. i live in a moderately bike friendly city but the bike-only lanes are still full of cars half the time.
    what would rainbow unicorn do?

  14. #14
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
    Posts
    47,276

    How do I break the "glass" speed barrier?

    Quote Originally Posted by jseko View Post
    After about 6000 miles, I've realized that my speed is not limited by how fast I can pedal my bike, but rather how fast motorists think I'm going, which is something like 10 MPH I think.

    On some parts of my commute, I can get my bike well over 20 MPH on a 25 MPH street, but even if I don't have a stop sign, cars will proceed through their stop sign or make a turn about 50 ft in front of me. From about 25 MPH, it probably takes me close to 100 ft to stop the bike if my math is correct so that is a big problem.

    Lights, steady, flashing, or both do not seem to help.
    Never stop pedaling, even if you are coasting. When your legs stop moving drivers seem to think you are yielding to them or slowing down.
    mtbtires.com
    The trouble with common sense is it is no longer common

  15. #15
    mtbr member
    Reputation: newfangled's Avatar
    Join Date
    Sep 2010
    Posts
    1,878
    I like to stand up in potentially confusing situations - I think it makes me look more scary, like a puffed up cat.

  16. #16
    mtbr member
    Reputation: BrianMc's Avatar
    Join Date
    Jan 2010
    Posts
    3,414
    Quote Originally Posted by jseko View Post
    I should note that I am only estimating the 100ft figure. I obtained the value of -4.8 m/s^2 for max acceleration for a bicycle on flat, smooth, dry, clean pavement from a document used for developing bicycle facilities. From that

    Guide for the Development of Bicycle Facilities, PDF file: https://bookstore.transportation.org...x?id=1180&DB=3
    At one intersection I often have to make last minute stops (hidden approaching traffic) from about 10-11 mph or about 4.8 m/sec. I travel no more than a meter doing so (my point of no return), and I think maybe closer to 0.5 m with a front brake wheelie as I dismount. That is a considerably shorter distance than their number gives. Of course, I can tolerate a bit of a front brake wheelie as I am dismounting. Less than a half-second. The butt behind the seat technique allows harder braking that would otherwise generate an OTB (and extended front brake wheelie, if you will). The deceleration maybe not up to my slow speed emergency stop, though. I have considerable road hugging weight which at the slow speed hasn't the kinetic energy of 25 mph (11 m/sec) so the extra traction and inertia to launch me comes into play. Given their old number, you stop in 2. 3 sec with an average speed of 5.5 m/sec (close enough), so travel about 12.6 M or 42 feet. Which is all the way through the intersection if there is two lanes and parking both sides. The new number is 2.4-3 m/sec/sec which comes out to 84 feet with the lower one. Close enough to 100. Maybe they include the time needed to react. That would be almost zero at known intersections, unless it was a complete not seeing the stop sign at all with a building hiding them.

    I have two places it might be safe to test this for me and my bike if traffic is light (no one coming either way for me to scare though I would be on the shoulder). It won't happen soon as I am prepping to a Habitat ride. I wonder if this number of theirs is designed around old hard pads (not cool stops) and hard tires and the delay to get on the brakes. Still, even if the old number is low by a factor of 2, you are still well over 20 feet to stop and that is clean through a 2-lane intersection with no parking lanes. Though you might get slow enough for an unplanned right or left turn (depending) to avoid hitting the car. It would be good to know so we can choose an option. On dry pavement, I can do a 20 mph corner, maybe faster. They won't see me before I T-bone them if I go straight, but they might notice me swoop in front of the car and at least get the driver helping to avoid the collision. Or I might swing around behind it they are getting the move on. Forewarned is forearmed.

    BrianMc

  17. #17
    mtbr member
    Reputation:
    Join Date
    Mar 2013
    Posts
    170
    I don't know if it's effective or not, but I generally odn't have problems so I guess it works, but I wear a military strobe light on my back pack. It's bright. Really, really bright. Think a camera flash going off every 1/2 second. Just as effective during the day too... And I do the puffed up cat pose like Newfangled...

  18. #18
    mtbr member
    Reputation: BrianMc's Avatar
    Join Date
    Jan 2010
    Posts
    3,414
    Standing to climb a hill dissuades a pass on a blind hill, it seems. I got another driver waiting for me and the only change has been the Glo rim skins. Maybe it just helps enough to punch into their awareness. No I don't slow or stop pedaling, but will add more speed if they are waiting for me.

    I had a Xenon flasher in amber (same as the blue ones on top of school buses here). I gave it away. Other than needing AA alkalines (3 NiHM a no-go) and eating them rapidly (maybe 3 hour run time) and sending out enough EMF to screw up my heart monitor, it was great. Too short lived a flash for me to get brightness readings on it, but it was way up there. It got respect. The flash interval dropped as the batteries got low to about 1 second. At 25 mph you go about 40 feet in that time, and if a driver blinks, he misses the flash. So it screamed for an external battery mod.

    BrianMc

  19. #19
    Mantis, Paramount, Campy
    Reputation: Shayne's Avatar
    Join Date
    Jan 2004
    Posts
    4,291
    Quote Originally Posted by jseko View Post
    From about 25 MPH, it probably takes me close to 100 ft to stop the bike if my math is correct so that is a big problem.
    I stopped from 21mph in less than 6 feet last night. If it would have taken 7 feet i'd be in the hospital.
    Front wheel locked and heels on the ground so i didn't go OTB.
    *** --- *** --- ***

  20. #20
    mtbr member
    Reputation: mtbxplorer's Avatar
    Join Date
    Dec 2009
    Posts
    5,168
    ^^ You mean like Fred Flinstone?

  21. #21
    mtbr member
    Reputation:
    Join Date
    Mar 2013
    Posts
    345
    That formula is probably not up to date with current brake technology is my guess, or it shows a "slowdown" rather than emergency brake + manuever thresholds.

    My particular method is forcing the drivers to stop if they don't want to run their cars off the road. My headlight / rear light are extremely bright.. not sure what the lumens are of them, but in daylight, in my garage, you can see the actual lightbeam

  22. #22
    mtbr member
    Reputation:
    Join Date
    Dec 2012
    Posts
    580
    I also use my 500mw Cree flashlight at night so even the biggest SUV yields when they see me coming. I bet their P.O.'ed when they realize I'm just a cyclist. During the daytime my cut-off, carbon-knuckled motorcycle gloves work like claws. I can actually see drivers looking at it and backing down.

    On topic though, I notice I get respect when drivers see me hauling ass trying to keep pace with traffic. But there are still a lot of drivers who will cut me off just because they can. I'm okay with that. I think I cut off more car drivers than they cut me off.

Similar Threads

  1. Replies: 12
    Last Post: 04-05-2013, 01:45 PM
  2. Taking a "break" in the middle of a training program?
    By Casual Observer in forum Endurance XC Racing
    Replies: 2
    Last Post: 12-29-2011, 11:59 AM
  3. Replies: 14
    Last Post: 11-24-2011, 10:32 AM
  4. New wheels "break in " period?
    By jhuffman in forum Wheels and Tires
    Replies: 9
    Last Post: 07-05-2011, 11:40 AM
  5. Industry Nine "Break In Service" wtf?
    By rydbyk in forum Wheels and Tires
    Replies: 22
    Last Post: 05-22-2011, 08:47 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •