3 ms·

Their research is fundamentally flawed...and it is rooted in an fruitless desire to optimize something that is physically unoptimizable. There is no sand-arrang

Their research is fundamentally flawed...and it is rooted in an fruitless desire to optimize something that is physically unoptimizable. There is no sand-arranging possibility that can cause the falling-rate of sand in an hourglass to change significantly.

seanmcdirmid 13y ago
Merging later encourages better utilization of road capacity and eliminates bottlenecks further away from the overloaded resource. It's quite simple really, in this case the polite behavior is wrong, and if everyone would just be greedy, the behavior would no longer be impolite and would be more optimal (source, I live in china, this really works better than the alternative, we have plenty of overloaded resources).
- saosebastiao 13y ago
  Every advocate always has their pet theory as to why their method works better than others. They also have "evidence" which is either completely anecdotal or does not control for even the most obvious of factors (such as rate of queue arrival or average speed in the constrained resource). Simply put, they are all wrong. A bottleneck is a bottleneck and there is no fairy dust magic queueing technique that works better than another. At best, some techniques might have a behavioral advantage...but I stress again, they are all inconsequential. We are talking tens of seconds of time savings at best.
  - icarus_drowning 13y ago
    Late merging makes better use of available road bandwidth. That's not anecdotal, that's simple math.
    - ronaldx 13y ago
      Late merging makes more effective use of the car waiting area, at the expense of a faster flow.
      - seanmcdirmid 13y ago
        So you mean the flow through a straw is better than through a funnel?
    - abstrakraft 13y ago
      Bandwidth is probably the wrong term here. It keeps traffic from backing up as far, true, but this really only matters to people who are turning off before the merge. Ignoring early exits, at steady state, the only thing that really matters is flow _after_ the merge - that's what determines the rate at which traffic passes the restriction.
  - seanmcdirmid 13y ago
    I would never try this myself mind you; I hate pissing people off in the road in the states and I'm happy to outsource my driving to a taxi driver in china. However, it's a simple matter of utilization, if everyone waited properly in line, traffic would seize up in Beijing as many intersections would become blocked by single lines of cars next to empty unused lanes. We are talking about saving minutes, 10s of minutes, or even days [1]. Funny how Americans haven't seen real traffic before and think they know the right global solutions. [1] http://www.npr.org/blogs/thetwo-way/2010/08/23/129376194/traffic-jam-beijing-tibet http://www.npr.org/blogs/thetwo-way/2010/08/23/129376194/tra...
jkubicek 13y ago
Assuming this is true, zipper merge is still a vastly preferable system. 1) It's a more effective use of the roadway. Why have 1 lane of traffic backed up for 2 miles when you can have 2 lanes of traffic backed up for 1 mile? 2) It's equitable. Everyone moves at the same speed, there's no way to game the system for personal advantage.
- ronaldx 13y ago
  It's not evident that this is a more effective use of roadway, as the article hints at. The problem is the bottleneck point, where people are obligated to move into one lane. This is what causes delay - the faster you can get cars moving through the bottleneck point, the less delays there will be behind. So it doesn't matter so much where the cars behind are positioned to wait. Zipper merge likely causes more delay - in practice - as there has to be a late negotiation over whose 'turn' it is to merge. If this negotiation is planned earlier, it doesn't need to have such an effect (in fact, I imagine it could eliminate all the delay) at the bottleneck point.
  - andrewflnr 13y ago
    I think the point of zipper merging is that the negotiation has, in fact, been planned a couple miles before the actual merge point, so that the cars are alternating like | _ _ _ | _ _ _ Then it's easy to condense to | _ _ _ _ _ _

seanmcdirmid 13y ago

Merging later encourages better utilization of road capacity and eliminates bottlenecks further away from the overloaded resource. It's quite simple really, in this case the polite behavior is wrong, and if everyone would just be greedy, the behavior would no longer be impolite and would be more optimal (source, I live in china, this really works better than the alternative, we have plenty of overloaded resources).

saosebastiao 13y ago
Every advocate always has their pet theory as to why their method works better than others. They also have "evidence" which is either completely anecdotal or does not control for even the most obvious of factors (such as rate of queue arrival or average speed in the constrained resource). Simply put, they are all wrong. A bottleneck is a bottleneck and there is no fairy dust magic queueing technique that works better than another. At best, some techniques might have a behavioral advantage...but I stress again, they are all inconsequential. We are talking tens of seconds of time savings at best.
- icarus_drowning 13y ago
  Late merging makes better use of available road bandwidth. That's not anecdotal, that's simple math.
  - ronaldx 13y ago
    Late merging makes more effective use of the car waiting area, at the expense of a faster flow.
    - seanmcdirmid 13y ago
      So you mean the flow through a straw is better than through a funnel?
  - abstrakraft 13y ago
    Bandwidth is probably the wrong term here. It keeps traffic from backing up as far, true, but this really only matters to people who are turning off before the merge. Ignoring early exits, at steady state, the only thing that really matters is flow _after_ the merge - that's what determines the rate at which traffic passes the restriction.
- seanmcdirmid 13y ago
  I would never try this myself mind you; I hate pissing people off in the road in the states and I'm happy to outsource my driving to a taxi driver in china. However, it's a simple matter of utilization, if everyone waited properly in line, traffic would seize up in Beijing as many intersections would become blocked by single lines of cars next to empty unused lanes. We are talking about saving minutes, 10s of minutes, or even days [1]. Funny how Americans haven't seen real traffic before and think they know the right global solutions. [1] http://www.npr.org/blogs/thetwo-way/2010/08/23/129376194/traffic-jam-beijing-tibet http://www.npr.org/blogs/thetwo-way/2010/08/23/129376194/tra...

jkubicek 13y ago

Assuming this is true, zipper merge is still a vastly preferable system. 1) It's a more effective use of the roadway. Why have 1 lane of traffic backed up for 2 miles when you can have 2 lanes of traffic backed up for 1 mile? 2) It's equitable. Everyone moves at the same speed, there's no way to game the system for personal advantage.

ronaldx 13y ago
It's not evident that this is a more effective use of roadway, as the article hints at. The problem is the bottleneck point, where people are obligated to move into one lane. This is what causes delay - the faster you can get cars moving through the bottleneck point, the less delays there will be behind. So it doesn't matter so much where the cars behind are positioned to wait. Zipper merge likely causes more delay - in practice - as there has to be a late negotiation over whose 'turn' it is to merge. If this negotiation is planned earlier, it doesn't need to have such an effect (in fact, I imagine it could eliminate all the delay) at the bottleneck point.
- andrewflnr 13y ago
  I think the point of zipper merging is that the negotiation has, in fact, been planned a couple miles before the actual merge point, so that the cars are alternating like | _ _ _ | _ _ _ Then it's easy to condense to | _ _ _ _ _ _