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Analysis of rounabout by simulation model (PTV Vissim).

  • 1.  Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-09-2019 03:01 PM

    Recently, we did a simulation of the roundabout in Peshawar, Pakistan by PTV Vissim due to the proposed roundabout faced delays and queues on a daily basis at peak hours, which we did to simulate the actual geometric design of that roundabout by collecting the data of vehicles passed through that specific roundabout by providing U-turns at every route before vehicles reaching for U-turns just in the roundabout. what we noticed is that these U-turns does not only provide smooth flow but also it increases the Level of Service from D to A. Therefore, we concluded in our paper that by providing U-turns on every route before vehicles reached to U-turns, can improve Level of Serviceability of any roundabout.


    Has anyone done similar research? If so, what have you found?

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    Muhammad Khan Aff.M.ASCE
    University Of Peshawar
    Peshawar
    9203482818190
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  • 2.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-13-2019 10:12 AM
    Muhammad,
    Can you provide a graphic of the roundabout showing where the u-turns were placed on the approach roadways?

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    Fraser Howe P.E., F.ASCE
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  • 3.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-13-2019 12:49 PM
    The U-turns are provided within the range of half a Kilometer. If you need my thesis and I can provide it. My thesis has all graphs and PTV Vissim analysis data table. Thanks

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    Muhammad Khan Aff.M.ASCE
    University Of Peshawar
    Peshawar
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  • 4.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-13-2019 05:52 PM
    Muhammad, The actual site conditions will determine if the propose u-turns will operate effectively on each approach:
    1. Are the roadways wide enough to allow vehicles to complete a U-turn? On US roads you need 3 receiving lanes for most vehicles to complete the turn.
    2. Can you provide a left-turn queue to accomodate the peak-hour U-turn volume, without backing-up into the left-most through lane?
    3. If the U-turn is located at, or near, a cross-street intersection, will the u-turns interfere with the cross-street operation?
    These are just a few of the considerations that will determine if a modeled scenario will not only improve the roundabout operation, but also not degrade the operation on the approach roadways.

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    Fraser Howe P.E., F.ASCE
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  • 5.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-15-2019 12:47 PM
    First of all, you are exactly right owing to originally we had two lanes which was the reason for queues and delays. What we have done is provided three lanes instead of two under existing geometry in PTV Vissim and got no delays and queues.
    Secondly, the vehicles take a smooth U-turn without any queues due to now we have three lanes. lastly, the U-turns are provided in the locality where there have streets and junctions because this place is located in Central Business District (CBD). Thanks.

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    Muhammad Khan Aff.M.ASCE
    University Of Peshawar
    Peshawar
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  • 6.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-20-2019 12:53 PM

    Good idea!  Low cost level of service improvement.  Looks like a candidate for useful universal information to include in the ASSHTO GDHS after your research is able to produce an application level design guide.  Yes, as Fraser Howe states there are many things to consider.  Not the least of which are approach speed, exit taper, turning path , entrance taper, flow gap, stacking capacity, sight distances, grades, weather conditions, and other design features normally used for intersections. Signage and enforcement would be included, as well as driver population characteristics (aggressive, moderate, casual).  Most likely prohibit trucks, buses and pedestrians.  Maybe bicycles as well.

    As with the normal GDHS presentations, please convert your simulations and research to practical NCN style (no computer necessary) designer-friendly tables, diagrams, and verbiage.  NCN style is best and quickest way for an experienced geometric designer to sketch before CADemizing it.

    I think an important factor missed by many designers is the 2-second rule of roadway conditions changes.  That is, try to provide a minimum of 2 seconds and as much as 6 seconds minimum driving time between roadway condition changes (such as lane width, lane drops, shoulder width, or other geometry) in order for the driver to adjust to the new condition.  Example distances are shown in the GDHS Decision Sight Distance tables.  This rule should determine the minimum distance needed between the u-turn and the roundabout.

    Hope you get some good help on your project.




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    Norman Voigt P.E., L.S., F.ASCE
    Pittsburgh PA
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  • 7.  RE: Analysis of rounabout by simulation model (PTV Vissim).

    Posted 08-23-2019 06:40 PM
    I did my research work through modern German software namely PTV Vissim and I have all values and tables including the level of serviceability, number of vehicles, speed, etc. I concluded my thesis by presenting a solution in my area. The solution is general and applicable to every roundabout.

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    Muhammad Khan Aff.M.ASCE
    University Of Peshawar
    Peshawar
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