4 ms·

Depends on many factors, including how much you value human life. Quoting from http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_672.pdf http://onlinepubs.tr

by dalke 11y ago

Depends on many factors, including how much you value human life. Quoting from http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_672.pdf http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_672.pdf : > The initial design and construction cost of a roundabout can vary significantly depending on the roundabout size, right-of-way impacts, illumination requirements, and other design or aesthetic features that may be desired. A new single-lane roundabout intersection in an unbuilt environment can have construction costs comparable to a traffic signal. However, as the size of the roundabout increases, particularly in a fully built-out commercial or residential area, the cost of roundabout construction can be higher than that of a traffic signal, depending on the footprint of the roundabout relative to that needed for the signal. However, the ongoing operations and maintenance cost of a roundabout can be less than that for a signal, with the possible exception of increased illumination needs for a roundabout. Although the initial construction cost may be more, a roundabout can have less operating and maintenance costs than a traffic signal, and the service life of a roundabout is significantly longer, approximately 25 years, compared with 10 years for a typical signal (2). Roundabouts also provide substantial cost savings to society due to the reduction in crashes, particularly fatal and injury crashes, over their service life. It also depends on how much you value people's time waiting for a light to change, as described in the parent scenario.

protomyth 11y ago
I guess I didn't phrase my question correctly, how much would it cost to replace all the traffic signals with roundabouts (per your original statement)? I am betting that would be cost prohibitive much less concerns for space.
- dalke 11y ago
  I didn't say "all", I said "most". Even countries with roundabouts also have traffic signals. My comment was not trying to establish what you are asking for. Instead, I was pointing out that there are many factors in addition to "cost to replace". There is also the yearly upkeep costs (power to the light, landscaping), signal timing maintenance every few years, and a shorter lifespan for signals vs. roundabout. Plus, of course, the savings in human time and lives. Then there's systemic issues which are harder to quantify. Roundabouts have higher throughput than signals, so switching to a roundabout might reduce the need to widen nearby parallel roads, which is an indirect cost savings. And roundabouts without signals work even when the power goes out. Quoting from http://www.roundaboutresources.org/when-should-roundabouts-replace-traffic-signals.html http://www.roundaboutresources.org/when-should-roundabouts-r... : > Roundabouts give superior traffic and safety performance to signalized intersections and to cross intersections almost everywhere, but roundabouts cost more, and not every signalized intersection or cross intersection is in great need of correction. Therefore, a highway agency should start at the top of its high-crash list and its high-congestion list and work down, often converting the problem location into an offset intersection where crossing flows are not too high. ... > The modern roundabout should be recommended not only as a retrofit where there are present safety and capacity problems, but also as an intersection in new construction where roads join or cross each other for the first time. That seems eminently reasonable to me. Recall too that the challenge was to "devise a traffic light that would not be monumentally inefficient and incompetent", so the question is, how much would that hypothetical system cost per intersection, vs. a known, good solution to the given problem?
  - WalterBright 11y ago
    > much would that hypothetical system cost per intersection, vs. a known, good solution to the given problem? Since the lights already exist, as well as cameras, and network connections, the incremental cost would be a box with a computer in it. The development cost of the software would be amortized over tens of thousands of intersections.
    - dalke 11y ago
      Yes, we are programmers, and are philosophically inclined to solve things through clever centralization. That doesn't mean it's the only, or the optimal solution. Roundabouts depend on decentralized control to achieve very similar goal. (Though without, by the way, the pretty nasty failure modes should that box, or the power, go down.) It's all handwaving without experimental studies and economic analysis. The numbers for roundabout are much better established than the smart systems, which are still experimental in nature. For that matter, how much is that cost? The proposal at http://readwrite.com/2014/01/22/ai-traffic-lights-intelligent http://readwrite.com/2014/01/22/ai-traffic-lights-intelligen... is "$20,000 to $40,000 per intersection" for 'a box with a computer in it'. From http://safety.fhwa.dot.gov/intersection/innovative/roundabouts/case_studies/fhwasa09018/ http://safety.fhwa.dot.gov/intersection/innovative/roundabou... , "The average construction cost of roundabouts is estimated at approximately $250,000". That gets its numbers from http://www.fhwa.dot.gov/publications/research/safety/00067/00067.pdf http://www.fhwa.dot.gov/publications/research/safety/00067/0... which says: > Recent roundabout projects in the United States have shown a wide range in reported construction costs. Assuming “1998 U.S. Dollars” in the following examples, costs ranged from $10,000 for a retrofit application of an existing traffic circle to $500,000 for a new roundabout at the junction of two State highways. National Cooperative Highway Research Program (NCHRP) Synthesis 264 (3) reports that the average construction cost of 14 U.S. roundabouts, none being part of an interchange, was approximately $250,000. This amount includes all construction elements, but does not include land acquisition. Elsewhere I gave links to places which said the installation costs for a roundabout were more expensive than signals. I don't know if the extra 5-10% price of the "box with a computer" changes the balance. I tried to get numbers for the cost of a intersection. from http://azdot.gov/business/engineering-and-construction/traffic/faq/pros-and-cons-of-traffic-signals http://azdot.gov/business/engineering-and-construction/traff...: > A modern signal can cost taxpayers between $80,000 and $100,000 to install, depending on the complexity of the intersection and the characteristics of the traffic using it. On top of this, there is the perpetual cost of the electrical power consumed in operating a signalized intersection 24 hours a day. This cost now averages about $1,400 per year. However, that appears to be for the dumb light, and not one with 'cameras and network connections' or even magnetic sensors. From http://www.masslive.com/news/index.ssf/2009/02/450000_traffic_light_cost_eyed.html http://www.masslive.com/news/index.ssf/2009/02/450000_traffi... : > A request to spend $450,000 to install a new traffic signal on Easthampton Road remains an option for the City Council. > And while the price tag might seem high for one traffic light, city officials insist that's the going rate to design and install such an item. > "They're smarter controllers than they ever were in the past," Department of Public Works Superintendent William D. Fuqua said yesterday. It's definitely not clear to me that the high-tech, interconnected system you desire is cheaper or more effective than roundabouts. (Again, there are clearly place where signals are more effective. I am not saying to only use rounabouts.) I would be happy to read any evidence you have which says otherwise. This also means I don't think you can call out "environmentalists" for not yet pushing for your high-tech dream to come to fruition. Mind you, some of those environmentalists are pushing for "complete streets", which is yet another way to achieve comparable goals of more effective use of public roads.

by dalke 11y ago

protomyth 11y ago

I guess I didn't phrase my question correctly, how much would it cost to replace all the traffic signals with roundabouts (per your original statement)? I am betting that would be cost prohibitive much less concerns for space.

dalke 11y ago
I didn't say "all", I said "most". Even countries with roundabouts also have traffic signals. My comment was not trying to establish what you are asking for. Instead, I was pointing out that there are many factors in addition to "cost to replace". There is also the yearly upkeep costs (power to the light, landscaping), signal timing maintenance every few years, and a shorter lifespan for signals vs. roundabout. Plus, of course, the savings in human time and lives. Then there's systemic issues which are harder to quantify. Roundabouts have higher throughput than signals, so switching to a roundabout might reduce the need to widen nearby parallel roads, which is an indirect cost savings. And roundabouts without signals work even when the power goes out. Quoting from http://www.roundaboutresources.org/when-should-roundabouts-replace-traffic-signals.html http://www.roundaboutresources.org/when-should-roundabouts-r... : > Roundabouts give superior traffic and safety performance to signalized intersections and to cross intersections almost everywhere, but roundabouts cost more, and not every signalized intersection or cross intersection is in great need of correction. Therefore, a highway agency should start at the top of its high-crash list and its high-congestion list and work down, often converting the problem location into an offset intersection where crossing flows are not too high. ... > The modern roundabout should be recommended not only as a retrofit where there are present safety and capacity problems, but also as an intersection in new construction where roads join or cross each other for the first time. That seems eminently reasonable to me. Recall too that the challenge was to "devise a traffic light that would not be monumentally inefficient and incompetent", so the question is, how much would that hypothetical system cost per intersection, vs. a known, good solution to the given problem?
- WalterBright 11y ago
  > much would that hypothetical system cost per intersection, vs. a known, good solution to the given problem? Since the lights already exist, as well as cameras, and network connections, the incremental cost would be a box with a computer in it. The development cost of the software would be amortized over tens of thousands of intersections.
  - dalke 11y ago
    Yes, we are programmers, and are philosophically inclined to solve things through clever centralization. That doesn't mean it's the only, or the optimal solution. Roundabouts depend on decentralized control to achieve very similar goal. (Though without, by the way, the pretty nasty failure modes should that box, or the power, go down.) It's all handwaving without experimental studies and economic analysis. The numbers for roundabout are much better established than the smart systems, which are still experimental in nature. For that matter, how much is that cost? The proposal at http://readwrite.com/2014/01/22/ai-traffic-lights-intelligent http://readwrite.com/2014/01/22/ai-traffic-lights-intelligen... is "$20,000 to $40,000 per intersection" for 'a box with a computer in it'. From http://safety.fhwa.dot.gov/intersection/innovative/roundabouts/case_studies/fhwasa09018/ http://safety.fhwa.dot.gov/intersection/innovative/roundabou... , "The average construction cost of roundabouts is estimated at approximately $250,000". That gets its numbers from http://www.fhwa.dot.gov/publications/research/safety/00067/00067.pdf http://www.fhwa.dot.gov/publications/research/safety/00067/0... which says: > Recent roundabout projects in the United States have shown a wide range in reported construction costs. Assuming “1998 U.S. Dollars” in the following examples, costs ranged from $10,000 for a retrofit application of an existing traffic circle to $500,000 for a new roundabout at the junction of two State highways. National Cooperative Highway Research Program (NCHRP) Synthesis 264 (3) reports that the average construction cost of 14 U.S. roundabouts, none being part of an interchange, was approximately $250,000. This amount includes all construction elements, but does not include land acquisition. Elsewhere I gave links to places which said the installation costs for a roundabout were more expensive than signals. I don't know if the extra 5-10% price of the "box with a computer" changes the balance. I tried to get numbers for the cost of a intersection. from http://azdot.gov/business/engineering-and-construction/traffic/faq/pros-and-cons-of-traffic-signals http://azdot.gov/business/engineering-and-construction/traff...: > A modern signal can cost taxpayers between $80,000 and $100,000 to install, depending on the complexity of the intersection and the characteristics of the traffic using it. On top of this, there is the perpetual cost of the electrical power consumed in operating a signalized intersection 24 hours a day. This cost now averages about $1,400 per year. However, that appears to be for the dumb light, and not one with 'cameras and network connections' or even magnetic sensors. From http://www.masslive.com/news/index.ssf/2009/02/450000_traffic_light_cost_eyed.html http://www.masslive.com/news/index.ssf/2009/02/450000_traffi... : > A request to spend $450,000 to install a new traffic signal on Easthampton Road remains an option for the City Council. > And while the price tag might seem high for one traffic light, city officials insist that's the going rate to design and install such an item. > "They're smarter controllers than they ever were in the past," Department of Public Works Superintendent William D. Fuqua said yesterday. It's definitely not clear to me that the high-tech, interconnected system you desire is cheaper or more effective than roundabouts. (Again, there are clearly place where signals are more effective. I am not saying to only use rounabouts.) I would be happy to read any evidence you have which says otherwise. This also means I don't think you can call out "environmentalists" for not yet pushing for your high-tech dream to come to fruition. Mind you, some of those environmentalists are pushing for "complete streets", which is yet another way to achieve comparable goals of more effective use of public roads.