8 votes

Microsimulation of Traffic Control: Onramp

4 comments

  1. skybrian
    Link
    From the info box:

    From the info box:

    This scenario demonstrates how an on-ramp acts as a stationary bottleneck provoking a traffic breakdown on the main road upstream of the on-ramp and free traffic downstream. With the initial settings, upstream propagating stop-and-go waves on the main road are triggered at the on-ramp region! The on-ramp acts as generator of the waves, but any other type of flow-restricting inhomogeneity ("bottleneck") could do the same. Just drag an obstacle on the road to see the effect.

    Now vary the traffic flows of the main road and the on-ramp.

    • At an reduced inflow of 2000 veh./h, free traffic can be sustained for up to 20 min but sooner or later breaks down.
    • At 1600 veh./h, no breakdown occurs, but an existing jam will not dissolve! This so-called hysteresis is the basis why traffic-control measures to prevent the breakdown have a huge application potential.
    • On increasing the ramp flow to 800 veh./h, and decreasing the main flow to 1600 veh./h, observe a stationary localized traffic breakdown "pinned" at the ramp region. Only for higher inflows, the upstream front will propagate further upstream giving rise to an extended congested region!
    • Play with the politeness factor and switching threshold to change the aggressivity of the ramp vehicles.
    2 votes
  2. [3]
    Icarus
    Link
    I can tell this is a simulation just by how many cars in the far right lane merge left one lane when a car is needing to merge from the on ramp. That never happens. In fact, just today I got on...

    I can tell this is a simulation just by how many cars in the far right lane merge left one lane when a car is needing to merge from the on ramp. That never happens. In fact, just today I got on the interstate, needed to merge over one lane since mine would shortly end, and the cars in the adjacent lane sped up after I turned my blinker on. The San Francisco Bay Area has by far the worst drivers out of any of the 10+ places I have lived in the US. Its really sucked the joy of driving I use to have when I drove mainly in the country.

    Oh wait this simulation has a meter called "Politeness". Turning that all the way down seems to simulate the situation here perfectly!

    1. [2]
      skybrian
      Link Parent
      Speeding up or slowing down can work, depending on the situation - the point is to get out of the way. But sometimes people make the wrong call. In rural areas I think it's more common to move...

      Speeding up or slowing down can work, depending on the situation - the point is to get out of the way. But sometimes people make the wrong call.

      In rural areas I think it's more common to move over one lane. In areas where the highway is constantly busy and people are used to congestion, it seems more likely that they will change speeds, and they'll only move over if the next lane is a lot less busy and yet seems safe.

      1. Icarus
        Link Parent
        Too often, I notice drivers in the SF Bay Area see a blinker as a sign they need to speed up and not let someone in front of them, even when its just normal lane changing! But I hear you, I was...

        Too often, I notice drivers in the SF Bay Area see a blinker as a sign they need to speed up and not let someone in front of them, even when its just normal lane changing! But I hear you, I was taught the best way to ease merging was to plan ahead and try to merge over if possible since its difficult to an on-ramps speed.

        I think another issue is a state like CA allows cars to pass on either the left or the right, whereas VA typically only allows left hand passing. This ensures traffic operates more predictably across lanes. If you are cruising in the far right lane, its easier to temporarily speed up to move into the left lane, then merge back into the right lane to resume the previous speed. In CA, you may merge over to allow someone to merge in, but the person behind you may just go ahead assume they can floor it.

        2 votes