Many aspects of the simulation are subject to stochasticity, controlled by
RNGs and the initial random seed (
https://sumo.dlr.de/docs/Simulation/Randomness.html).
After running the simulation for some time, the RNG is in a particular
configuration and you can only reproduce that situation by also restoring
this RNG configuration.
Here are two possible solutions:
1) Use the the initial setup as you are doing now but sample a larger
configuration space by running with different values for the --seed option
until you find a situation of interest (which may not be the exact
situation you had originally but nevertheless suitable to your purpose).
2) Use the built-in facilities for restoring simulation state including
RNG:
https://sumo.dlr.de/docs/Simulation/SaveAndLoad.html
https://sumo.dlr.de/docs/Simulation/SaveAndLoad.html#random_number_generators_rng

regards,
Jakob

Am Fr., 16. Juni 2023 um 08:58 Uhr schrieb Kherroubi Zineelabidine <
[email protected]>:

> Hi all,
>
> I have a simulation of an accident scenario that occurs at the 16000th
> simulation time-step. I would like to generate this same accident scenario
> (same geometry, same vehicles, same vehicles speed behaviors and
> trajectories) in a new simulation (at the beginning time step instead of
> waiting until 16000 as in the original simulation).
> For that, I saved all the vehicles' states in the original simulation of
> accident:* Position, speed, acceleration, type, angle, speed_factor,
> speed_deviation, lane_id, lane_position*.
>
> In the new simulation, I added the vehicles from the accident scenario:
> *1- traci.vehicle.add(vehID ,routeID ,departSpeed,typeID, departPos=0)*
>
> then, for each vehicle , and before executing a simulation step, I
> adjusted the state of vehicles as in the original scenario accident:
>
>
>
> *2- traci.vehicle.setAccel(vehID ,accel)3-
> traci.vehicle.setSpeed(vehID,speed)4-
> traci.vehicle.setSpeedFactor(vehID,factor)5-
> traci.vehicle.moveTo(vehID,laneID,pos) *
>
> There is only one vehicle that I control through traci using the same
> rule-based control function as in the accident scenario.
>
> However when I run this new simulation, no accident happen and the
> trajectories of vehicles are different from the original accident scenario. I
> thought that I included all the information to reproduce the original
> accident scenario, especially the *vehicle type* and *speedFactor *(where
> I forced *speedFactor Deviation *to 0).
>
> *Why is the new scenario different from the original ?*
> *How to reproduce the same scenario using initial vehicle states ?*
>
> Best regards,
> *________________________*
>
> *Zine el abidine KHERROUBI*
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