Today’s Headlines

  • Dean Skelos Sentenced to Five Years in Prison (NYT, Politico); Preet: I’m Not Done (Politico)
  • Paul White, Tom Wright, Joe Lhota Among Those Enlisted to Shepherd de Blasio Streetcar (AMNY, DNA)
  • Gotham Gazette Explains What a “Self-Financed” BQX Would Really Mean
  • Reliable Trains and Buses, Not Gimmicks, Are What New Yorkers Want From Transit (2AS, Freemark)
  • Tri-State: NJ Transit Problems Go Deeper Than Inadequate Funding (MTR)
  • Parking Crusader Vincent Gentile Rushes to Aid Motorists Ticketed for Blocking Curb Ramps (Post 1, 2)
  • Related: Imagine NYPD’s Failure to Enforce Law Against Crosswalk Killings Getting This Much Coverage
  • Motorist Flips Car and Dies After Being Shot in Canarsie (Post)
  • Cop Who Told Driver What Police Think of Vision Zero Now Monitoring Security Cameras (Post)
  • Crossing Guards Get Some Love in Park Slope (Bklyn Paper)
  • Jason Gay to America: Cyclists Are People, Too (WSJ)

More headlines at Streetsblog USA

  • Vooch

    bikes move 7 times as many people as cars in same space

    it’s cars that have proven not to be ‘scale able ‘

    if you want the East river bridges to carry more people you should reduce cars to 1 lane at most. Since cars were allowed on East River Bridges capacity has plummeted.

    600 bikes per peak hour on WB bridge is a real number.

    so on WB bridge, cyclists are 25% of roadway traffic with 3% of soace.

  • AMH

    It’s not remotely OK, but it’s now legal.

  • Andrew

    Not anymore. They used to be unmarked crosswalks. Then the law changed in 2009 to redefine an unmarked crosswalk to exclude these cases at T-intersections, in the name of parking.

    The law should never have been changed. And now it should be changed back.

  • sbauman

    I’ve examined the Citibike data. There were approximately 1000 trips from within 1/4 mile of Union Square to within 1/4 mile of Oasis. The average travel time was 30 minutes. N.B. only trip times between 10 minutes and 2 hours were considered to avoid incorrect data.

  • Joe R.

    The gradient often matters more than the actual number of feet climbed. The worst gradient on 5th Avenue according to your numbers would be around 2%. Not sure what the gradients are on the bridges but I’d say 3% or less simply because fully-loaded trucks need to negotiate them. Most cyclists will barely notice an 0.5% gradient. Indeed, they could probably climb Mt. Everest if you have a ramp going that high which never exceeded 0.5%. 1% starts to get noticeable but still not too bad. 2% might be where you’ll start to really exert yourself, 3% more so. Steeper climbs get you into aerobic deficit sooner. The actual number of feet you climb only matters if you’re still doing the climb long enough to go into aerobic deficit. A shorter but steeper climb is often worse for a cyclist than a longer but shallower climb. On one of my usual routes I’ll climb about 70 feet in maybe 2 miles. It’s not a steady uphill but I’d say maybe half of it is climbing. I don’t go much above my average effort and feel just fine when I’m done. There’s another route where I climb 60 feet in about 6 blocks. Less climbing feet, but I’m spent when I reach the top. It takes me a few blocks to recover.

    I’ll grant the bridges are undoubtedly a worse climb for cyclists than anything on 5th Avenue, but my point is number of feet climbed isn’t the sole determinant here. If the bridge approaches were 3 miles long, cyclists would scarcely notice the climb.

  • Joe R.

    30 minutes still beats the competition by over 20 minutes.

  • sbauman

    I agree. I just wanted to derive a bicycle travel time based from something other than a dedicated cyclist’s perspective.

  • sbauman

    I’ve given up trying to rate climbs, slope vs. height gain, etc. It’s as productive as arguing about religion. I’ve made it a practice to follow the French example. I give the total distance and the total amount of climbing.

    A few years back, a friend asked me to evaluate his club’s criterion for rating climbing difficulty on rides. Their criterion was average gradient. They took every gradient and multiplied it by the distance covered, added up the total and divided by the total miles. I pointed out that computationally, this was equivalent to taking the total climbing elevation and dividing by the total distance. Maybe, the French were on to something.

    The gradient on the Williamsburg Bridge is steeper on the bike/pedestrian path than on the roadway. Both start at the same point. However, by the time the anchorages are reached, the bike/ped path is on the upper level. The amount of climbing is about 20 feet greater for the bike/ped path. It’s even worse for the pedestrian path on the Brooklyn side.

    The pedestrian (south side) path starts at Driggs Ave not S 5th Place. This ramp has rest areas meaning it’s probably 8%. Sorry, I’m too lazy to look up the ADA regulations. This is approximately the same climb before the path was rehabilitated. The only difference is the old path went straight up from Driggs to the upper level at the Brooklyn anchorage.

  • Joe R.

    My own personal rating is how spent I feel when I reach the top. That’s really all that matters, not some theoretical amount of climbing feet or average gradient. To make matters even more complicated, some climbs usually have headwinds while others have tailwinds. I agree trying to rate climbs is probably a fool’s errand. I just know when I’m riding which ones are worth taking a longer route to avoid and which aren’t.

    I don’t think NYC considers climbs at all when it lays out its bike routes. Some of the bike routes by me are on the steepest streets.

  • Vooch

    there are 1,000 Citibike daily trips from Union Square to 1/4 of Oasis ? That’s a powerful statement of the utility of cycling.

  • Vooch

    Commuter cyclists ride much slower than their max speed. Therefore, gradients do not matter all that much for commuters, they just exert a itty bit more effort.

    on ther other hand, Grades mean a lot to Freds who are always trying to max speed.

    ADA ramps are less than 1:12

  • AnoNYC
  • ahwr

    Most cyclists will barely notice an 0.5% gradient. Indeed, they could probably climb Mt. Everest if you have a ramp going that high which never exceeded 0.5%.

    How long would the ramp be compared to how many miles a typical cyclist rides in a year?

  • sbauman

    I’m sorry, if I wasn’t clear. There were 1000 such trips from the start of Citibike until the end of March 2016. That’s all the trip data that can be downloaded from the Citibike site.

  • ahwr

    Peak two way bike volumes over the WB bridge is 6-7pm, 885 bikes according to 2014 Hub Bound. But the capacity of a two way bikeway in your chart is 7500/hour. Does that lane feel like it can serve 8.5x as many bikes as it does now at peak?

    In the general traffic lanes per lane peak throughput outbound is 1094 people outbound, 975 people inbound in cars/trucks/taxis/vans.

  • ahwr

    Commuter cyclists ride much slower than their max speed.

    They ride slower than their max speed? Or they ride at less than full effort? Whenever I bike during commute hours I see people slow down on hills of any length, like on the east river bridges. Gradients do matter.

  • sbauman

    Here’s the spec regarding intermediate landings:
    (d) Landings. Ramps having slopes greater than one vertical to 15 horizontal shall have landings at the top and bottom and at least one intermediate landing shall be provided for each 5 feet of rise. Top landings and intermediate landings shall have a dimension measured in the direction of ramp run of not less than 5 feet. Landings at the bottom of ramps shall have a dimension in the direction of ramp run of not less than 6 feet.

    The south side Brooklyn ramp has intermediate landings. Therefore, its slope is between 6.7% and 8.3%. The other ramps don’t. Therefore, their slope is less than 6.7%

  • Vooch

    if WB bridge peak hour cycling traffic was 885 in ’14, it’s likely just shy of 1,000 this year.

    the NATCO slide is based on same width of roadway – 7,500 cyclists could easily ride over WB bridge peak hour using the width of 2 car lanes. If we want to increase throughout on WB bridge, we’d convert 6 of the 8 motor lanes to bus only lanes.

    you are also using the debunked 1.6 person per car number which exagerates carrying capacity of NYC motor lanes.

  • ahwr

    you are also using the debunked 1.6 person per car number which exagerates carrying capacity of NYC motor lanes.

    Nope, 1.21-1.31.

    People: 3335 inbound, 4263 outbound 5-6pm

    Vehicles: 2736 inbound, 3237 outbound 5-6pm

    the NATCO slide is based on same width of roadway – 7,500 cyclists could easily ride over WB bridge peak hour using the width of 2 car lanes.

    Same width of roadway would be one car lane, not two.

    The capacity of a single 10-foot lane (or equivalent
    width) by mode at peak conditions with normal

    Can you imagine 7500 cyclists per hour – 8.5x the fall 2014 usage, 7.5x what you think usage is now – on the Williamsburg Bridge bike path? It’s probably about ten feet wide. Not sure the NACTO chart is realistic. Or if it is, that it applies here.

  • sbauman

    I find NACTO’s assertion that a 10 ft. wide protected bike lane can handle 7,500 in two directions difficult to believe. Here’s why.

    1. The defensive driving safe distance criterion between cars is 3 seconds. This is based on a 1 second reaction time + 2 second braking time. There’s no reason why average cyclists and drivers should have different reaction times. Bicycle brakes are not as good as car brakes. Accepting the 3 second spacing implies 1200 bikes/hour for each line of bikes.

    Approximately 3 bikes can fit side by side within a 10 foot wide lane.

    This brings the rate up to 3600 bikes/hour. That’s roughly half of NACTO’s figure.

    2. Bicycle counts were taken during the 1980 subway strike on the exclusive bike lanes that were set up. These rates were remarkably consistent: 4000 bikes/hour. The rates were taken on the Queensboro Bridge and the exclusive bike lanes on 6th and 7th-Bway-5th Aves.

    3. The Five Boro Bike Tour provides another laboratory test for evaluating bike lane capacity. Approximately 30,000 cyclists pass the 30 ft. wide start line within a 2 1/2 hour period. That comes to 4000 bikes/hour per 10 ft wide lane. Releasing bikes at greater rates resulted in traffic jams when the roadway was compressed to 30 feet in Central Park.

  • Vooch

    cyclists stop in 1/100 the distance of drivers

  • sbauman

    The physical limitation on bicycle braking is discussed in DeLong’s Guide to Bicycles and Bicycling, Fred DeLong, 1974, Chilton Book Company, pp. 206-212. It’s the only explanation of the physics that I’ve seen in a bicycling book. The explanation is at a level that is taught in high school physics – principle of levers. The principle applies to all two axle vehicles, e.g. passenger cars.

    Essentially, on flat level pavement the maximum braking deceleration < (l/h)g, where l is the distance of the center of mass behind the front wheel axle, h is the height of the center of mass above the ground and g is gravitational acceleration.

    Assuming that a typical car has a 105" wheelbase and a 60%-40% front-rear weight distribution, the car/passenger center of mass is 42" behind the front wheel axle. The car/passenger center of mass is typically below the height of the tire (max 15"). Therefore the a car's l/h ratio is typically 42/15 or close to 3.

    The bike/rider center of mass is typically over the bottom bracket. The bottom bracket is typically 24" from the front axle. The bike/rider center of mass is typically 48" above the road. Therefore, the bike/rider's l/h ratio is typically around 24/48 or 0.5.

    One should comfortably conclude that a bike/rider combination's maximum braking rate is only 1/5 to 1/4 that of a car/driver combination. This is even more reason for a biker to adhere to the 3 second defensive driving rule for separation between bikes.

  • Vooch

    a car driving at (typical NYC driving speed of) 35 mph stops in 140 feet

    a cyclist riding at (typical NYC riding speed of ) 11 MPH stops in 4’6″

    I was wrong the typical NYC cyclist stops in 1/30th the distance of a NYC driver

    Also note, that a drivers needs more than 1/2 a block to stop. No wonder drivers are killing so many people in crosswalks.

  • Joe R.

    For bikes I would probably use 1/2 second reaction time since your hands are already often covering the brakes or very near them. Also, reaction time of your hands is much faster than your legs.

    The 2 second braking time for defensive driving criteria isn’t based on stopping distances. It takes way longer than 2 seconds to stop from 80 mph on the highway. Rather, it’s based of differential braking rates, like when you have a sports car in front of an 18-wheeler. If all vehicles had similar deceleration rates and equally capable drivers, you would only need to take reaction times into account.

    In the case of bikes I’d say worst case you’re looking at a stopping distance of maybe ~30 feet based on a cruising speed of 14 or 15 mph and a deceleration rate of 5 mph/sec (not hard to do that on a bike—I’ve managed 15 mph/sec modulating my front brake). 30 feet equates to 1.5 seconds at typical bike cruising speeds. Add the half second reaction time and you can comfortable space bikes 2 seconds apart. This gets you ~5400 bikes/hour in a 10-foot lane.

    NACTO’s figure might be based on cyclists who commute regularly, hence are more skilled. The most skilled cyclists can run half a second apart or less in a pace line. Unskilled cyclists might be closer to 2-3 seconds. Regular commuter cyclists probably fall somewhere in the middle, perhaps around 1 second apart.

    All that said, note these are theoretical maximums. Just as with auto traffic, they’re rarely reached. However, the relative magnitudes still apply. On average 10 feet of bike lane will move 5 to 15 times more vehicles per hour than 10 feet of car lane.

  • Joe R.

    The car’s deceleration rate is limited by tire adhesion long before you reach the theoretical maximum given by your equation of ~3g. Some race cars can manage those kinds of decelerations with very sticky tires but the best street cars are lucky to do perhaps 1.2 or 1.3g.

    A skilled rider will shift their weight backwards and also hunch down in a panic stop. This moves the center of gravity down and back. As I’ve mentioned above, I’ve managed to achieve 0.7g in panic stops doing this. If you want to assume 0.5g is the maximum, you’re still getting at stopping distance of about 15 feet from 15 mph. This equates to 0.7 seconds spacing at 15 mph. Add 0.5 seconds for reaction time and you can safely space bikes 1.2 seconds apart at 15 mph. That’s 3000 bikes/hour.

  • Joe R.

    Obviously the thing about Everest is a theoretical construct. The ramp would need to be about 1200 miles long, plus I’m not even bothering to account for the fact the air will be unbreathable long before you reach the summit. In a world where atmospheric pressure was the same at 6 miles up as at sea level, plus cyclists could ride 24/7, they would barely notice they’re climbing on the way to summitting Everest if we kept the grade to 0.5%.

    Yeah, given the time the East River bridges were built trucks weren’t even on the radar. Looks like 4% grades which is pretty nasty after a block or two.

  • ahwr

    NACTO’s figure is based on this paper.

    On average 10 feet of bike lane will move 5 to 15 times more vehicles per hour than 10 feet of car lane.

    Theoretically? Or in practice?

  • Vooch

    the money quote in the academic paper states the general consensus for a 1m to 1.2m wide bike path is a capacity of 2,000 to 3,500 cyclists per hour.

    That jives with a NATCO figure of 7,000/hr for a 3 1/2 m wide bike path

  • sbauman

    There are several problems comparing the results of the Zhou et al report cited by NACTO to what’s present in NYC.

    1. E-Bikes composed 49% to 67% of the bikes used in all the bike lanes measured. The authors noted that capacity decreased with the percentage of e-bikes. The authors did not explore what capacity would be if the e-bike percentage were around 5%.

    2. The authors measured instantaneous not average capacity. The usual method for measuring capacity is to count the number of bicycles over at least 15 minutes. The measurement period used in the Zhou et al paper was 8 to 20 seconds. Their reason was “bicycle traffic flow cannot be observed under continuous saturated state in 15 minutes”.

    One reason that their “continuous saturated state” cannot be observed is that it cannot be sustained. There’s very little problem supplying a sufficient number of bikes on a continuous basis to support a “saturated state.” The problem is maintaining such flow downstream of the injection point for an indefinite length of time.

    The authors noted that their capacity measure decreased linearly with the sample period. One capacity measure was 2830 @ 8 seconds and 2590 @ 20 seconds, for a capacity decline of 20/sec duration. Extending the slope would imply 0 flow @ 236 seconds (almost 4 minutes).

    What really happens is that the flow levels out (becomes constant) for sample periods greater than some sample period. This lower limit is the sustainable peak flow rate. That’s the figure that should be used for capacity.

    3. The authors are implicitly assuming a grade separated bike lane to achieve such flow. Any route that would be scaled up for an L Train alternative would require bikes to stop for traffic lights. Unless the bike lane width expands to accommodate the stopped bikers, the capacity will be reduced by the green duty cycle.

    The figures in the Zhou et al paper should not be extrapolated to a continuous flow on NYC streets for these reasons. A better approach would be to use actual data from the few occasions where there was a sufficient number of cyclists to maintain saturated flow for a reasonably long duration.

  • Vooch

    actual data from many sources is referenced in the money quote.

    Even used Swedish data – and swedes are not known for BS