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Re: [sumo-user] Simulation is not using the specified Wiedemann Model
Hello,
You could compare the formula for your manual computation with the one in lines 109-153 at https://github.com/DLR-TS/sumo/blob/master/src/microsim/cfmodels/MSCFModel_Wiedemann.cpp

However, I think you have stumbled upon a bug that was first recorded in 2014 (https://github.com/DLR-TS/sumo/issues/1351).
As you may guess from that date, we do not use the Wiedemann model very often.
What it boils down to, is that the actual deceleration was bounded by the 'decel' attribute of the vType instead of the 'emergencyDecel' attibute (the emergencyDecel attribute represents the physical limit of braking and was not yet available 2014).
The bug is now fixed in the development version (binaries updated tomorrow at http://sumo.dlr.de/wiki/Downloads#SUMO_-_Latest_Development_Version).
Note, that in some situations your value of emergencyDecel="5.5" is not sufficient to ensure accident free driving.

regards,
Jakob

2018-03-19 21:13 GMT+01:00 Quinton Velcic <velcic@xxxxxxxxxxx>:
How do I make sure that the simulation is using the Wiedemann Model?

In my simulation this is how I am defining the Wiedemann model:

        <vType id="car1" vClass="passenger" accel="1.4" decel="1.8" length="4.64" maxSpeed="33" color="1,1,1" carFollowModel="Wiedemann" tau="1.0" security="1.0" estimation="1.0" emergencyDecel="5.5" apparentDecel="5.0"> 
</vType>

But the vehicle that uses this vType does not move according to the Wiedemann model.

In this picture "EXT" is the vehicle which has been assigned "car1" from above and "Ford1" is the leader of "EXT" which is moving according to a predefined speed via TraCI.

According to my manual calculations, the speed difference (dv) becomes greater than the threshold (sdv) at time step 81, so it is expected that the driver "EXT" should decelerating in the next time step. But as you can see this does not happen and the driver begins to decelerate at time step 89 resulting in the collision. 

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