Re: A a Vision Zero Town Hall Meeting (292469) | |||
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Re: A a Vision Zero Town Hall Meeting |
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Posted by Stephen Bauman on Fri Apr 18 11:47:18 2014, in response to Re: A a Vision Zero Town Hall Meeting, posted by BrooklynBus on Wed Apr 16 15:44:42 2014. Why are you willing to accept even a 5% chance of death with a 20 mph speed limit? Isn't it worth saving even one more life if we lowered the limit to 10 mph on every road?There are many ways to lower pedestrian fatalities. No single one will eliminate all (or nearly all). It becomes increasingly more difficult to get the same proportional benefit by continuing to go back to the same well. There's a sweet spot on the curve. Going from 50 mph to 40 mph reduces the fatality rate by 15% (100% to 85%). Going from 40 mph to 30 mph reduces fatality rate by 47% (85% to 45%). Going from 30 mph to 20 mph reduces fatality rate by 89% (45% to 5%). Reducing impact speed further will not result in such a dramatic reduction in either relative or absolute terms. Other means will have to be employed to significantly reduce the remaining 5%. The way to discover that method is to look for anomalies in fatality data. One possible area is to note that impacts with SUV's, trucks and buses result in higher fatality rates than with passenger cars for a given impact speed. Vehicle design changes can address this. However, such design changes are long lead for both design and implementation. Moreover, they are beyond NYC's control, except for NYC-owned vehicles. That does not make me against such changes. I'm being realistic in what can be accomplished today and what will take 5 years to become effective. Dangerous is exactly what it sounds like-- likely to cause injury or damage. What about the severity of injury or damage? Does that enter into your definition of dangerous? What about who is injured? There would not be much demand for action, if injuries were limited to those within the vehicles. Driver injuries could be overlooked because of the assumed risk doctrine. I'm not sure what you mean by modest braking rate. I don't know how I could be more specific. I stated that 10 fps/sec (6.7 mph/sec) was moderate braking. By contrast, panic braking rates while not skidding or losing control is around 25 fps/sec (17 mph/sec). Stopping for red lights uses the moderate braking rate so as not to encourage rear end collisions. I have had many instances where I am going at the speed limit and sometimes slower when I have had to use considerable force to stop and even then I am a few feet into the crosswalk and have to back up. Everything you have said in defence of going faster than the speed limit, not obeying stop signs, etc. indicates that you are a bad driver. Not being able to stop before a crosswalk while obeying the speed limit, does not contradict this observation. :=) Does your 3 seconds of amber take into account someone going downhill and needing a greater distance to stop? The 3 seconds is not my standard. It was issued by the Institute of Traffic Engineers (ITE) and was adopted as the standard for the yellow change interval by the Federal Highway Administration (FHWA). This standard does take grade into account both uphill and downhill. However, it's not likely to make much difference. You will need a grade of 7.8% to add 1 second to the yellow change interval. You do not see such grades in relatively flat NYC. So DOT allows like three or four seconds where both sides are red to allow cars to get across the intersection. That's called the red-clearance interval. The default setting for NYC is 2.0 seconds and has been for some time. It's also an ITE standard that's been adopted by the FHWA. That's good for 90 feet of combined road width plus vehicle length at 30 mph (45 ft/sec). I don't understand where your 11% comes from. It's the sum of the yellow change plus the red clearance intervals as a percentage of the total cycle time. For most NYC traffic signals, this comes to 10 seconds for the two yellow change and read clearance intervals per cycle and a 90 second cycle time. 10/90 = 11%. This assumes drivers after processing the green to yellow change will apply the brakes and not gun the accelerator. :=) There is a lot we can do to reduce accidents like having warning signs before merges and lanes that suddenly become left turn lanes and you have to make a sudden lane shift to get out. We also have lanes that disappear without warning. Poor and improperly placed signage, dark stretches of road, missing lane and directional markings. There is a lot we can do to reduce accidents like having warning signs before merges and lanes that suddenly become left turn lanes and you have to make a sudden lane shift to get out. We also have lanes that disappear without warning. Poor and improperly placed signage, dark stretches of road, missing lane and directional markings. I agree. However, what you described rarely involves a collision with a pedestrian. It's mostly vehicle-vehicle collisions. Stop thinking about fender benders and consider only pedestrian fatalities and injuries. But it is so much easier just to blame everything on speeding and blame the drivers even when speeding is not the cause, than for DOT to do a proper job to make the roads safe. A review of the pedestrian fatality police reports indicates the driver responsible 70% of the time and solely responsible 53% of the time. The two major causes are speeding and failure to yield. "The fault dear Brutus lies not in the stars..." More importantly, the quickest solution involves reducing impact speed. |
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