1). No. This is the estimated brake gap at the current vehicle speed
(vehicles within this distance are safety-critical). See also traci.vehicle.
2). The function returns the leader *and* the actual gap so you have full
control over the leader vehicles you wish to consider. Basically, dist is
only a labor-saving parameter to avoid searching too far.

regards,
Jakob

Am Mo., 4. Jan. 2021 um 11:05 Uhr schrieb Hriday Sanghvi <[email protected]>:

> Hello Jakob,
>
> Thank you for your reply. I was able to use subscribe Leader to get the
> required information. My only question is regarding the "dist" parameter
> which I read about here
> <https://sumo.dlr.de/pydoc/traci._vehicle.html#VehicleDomain-getLeader>.
> It states that
>
>> The dist parameter defines the minimum lookahead, 0 calculates a
>> lookahead from the brake gap.
>
> 1. Is the *brake gap *mentioned here the same as *minGap *parameter?
>
> Note that the returned leader may be further away than the given dist and
>> that the vehicle will only look on its current best lanes and not look
>> beyond the end of its final route edge.
>
> 2. I'm not sure what kind of behaviour this would entail. When they say
> that the returned leader may be further away than the given dist - what are
> the cases when this happens? Is there any way to control it?
>
> Thank you for your help.
>
> Sincerely,
> Hriday.
>
> On Sun, 13 Dec 2020 at 22:18, Jakob Erdmann <[email protected]> wrote:
>
>> You can use vehicle.getLeader and vehicle.subscribeLeader.
>>
>> Am So., 13. Dez. 2020 um 19:30 Uhr schrieb Hriday Sanghvi <
>> [email protected]>:
>>
>>> Hello Jakob, thank you for the update. I was actually trying to figure
>>> out which car is in the "front" and which car is in the "back" during a
>>> collision, since I need to manipulate the speeds based on that. What I am
>>> doing in the case where the vehicles collide when they are on the same
>>> lane, is using lane position to figure out the ordering. But for cases
>>> where the cars collide while they are on different edges (and hence
>>> different lanes), I have still not come up with a workaround. Tried using
>>> addSubscriptionFilterLeadFollow
>>> <https://sumo.dlr.de/pydoc/traci._vehicle.html#VehicleDomain-addSubscriptionFilterLCManeuver>
>>>  but
>>> it did not detect any of the vehicles. Any suggestions?
>>>
>>> Thank you.
>>>
>>> Sincerely,
>>> Hriday.
>>>
>>> On Sat, 12 Dec 2020 at 16:44, Jakob Erdmann <[email protected]>
>>> wrote:
>>>
>>>> Sorry, this isn't yet working (
>>>> https://github.com/eclipse/sumo/issues/7648).
>>>> Subscribe to this issue to be noticed when it is implemented.
>>>>
>>>> Am Do., 10. Dez. 2020 um 18:54 Uhr schrieb Hriday Sanghvi <
>>>> [email protected]>:
>>>>
>>>>> Hello Jakob,
>>>>>
>>>>> Thank you so much for your reply! I am trying to use the traci
>>>>> constant DISTANCE_REQUEST in order to be able to verify the distance
>>>>> between two vehicles by air/driving but I need to be able to pass some
>>>>> parameters to it. From what I see in *subscribeContext's function
>>>>> signature, *I think it would be passed to the "parameters" argument
>>>>> as per the doc
>>>>> <https://sumo.dlr.de/daily/pydoc/traci.domain.html#Domain-subscribeContext>.
>>>>> How do I find out what data type/structure it is passed as though? (For
>>>>> example, as a dictionary?). Could you please point me to the right
>>>>> resource/link? I really appreciate your help and feedback!
>>>>>
>>>>> Thank you.
>>>>> Sincerely,
>>>>> Hriday.
>>>>>
>>>>> On Thu, 10 Dec 2020 at 09:42, Jakob Erdmann <[email protected]>
>>>>> wrote:
>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> addSubscriptionFilterFieldOfVision must be set directly after a call
>>>>>> to vehicle.subscribeContext. It will use the range of that subscription 
>>>>>> and
>>>>>> filter it by angle.
>>>>>>
>>>>>> 1) upstream and downstream dist are measured in m along the route of
>>>>>> the vehicle
>>>>>> 2) unfortunately, no.
>>>>>> 3) Filters are meant to be combined so that each filter can further
>>>>>> reduce the set of returned vehicles.
>>>>>>
>>>>>> regards,
>>>>>> Jakob
>>>>>>
>>>>>> Am Mi., 9. Dez. 2020 um 19:56 Uhr schrieb Hriday Sanghvi <
>>>>>> [email protected]>:
>>>>>>
>>>>>>> Hello Jakob,
>>>>>>>
>>>>>>> Thank you for your response. I have tried using
>>>>>>> addSubscriptionFilterCFManeuver
>>>>>>> <https://sumo.dlr.de/daily/pydoc/traci._vehicle.html#VehicleDomain-addSubscriptionFilterCFManeuver>
>>>>>>>  instead
>>>>>>> of addSubscriptionFilterFieldOfVision
>>>>>>> <https://sumo.dlr.de/daily/pydoc/traci._vehicle.html#VehicleDomain-addSubscriptionFilterFieldOfVision>
>>>>>>>  since
>>>>>>> the latter only mentioned an "angle" and not a range. I also tried using
>>>>>>> addSubscriptionFilterTurn
>>>>>>> <https://sumo.dlr.de/daily/pydoc/traci._vehicle.html#VehicleDomain-addSubscriptionFilterTurn>
>>>>>>> .
>>>>>>>
>>>>>>> I receive an empty result in my subscriptions after 
>>>>>>> *addSubscriptionFilterTurn
>>>>>>> *and end up with a TraCI connection error. For
>>>>>>> *addSubscriptionFilterCFManeuver*, I also get an empty result in
>>>>>>> subscriptions unless I set an absurdly high downstreamDist value like 
>>>>>>> 1000.
>>>>>>> With regard to that, I just wanted to clarify the following if possible:
>>>>>>>
>>>>>>> 1. Is the downstreamDist a radial range/distance measured in metres
>>>>>>> in the direction towards the route that the ego vehicle is following?
>>>>>>> 2. Is there any way to "highlight" the range/distance using sumo-gui
>>>>>>> so I can see what it will and will not detect?
>>>>>>> 3. I think it is possible to chain multiple filters line by line? -
>>>>>>> I tried it and there was no error as such, but I just need a 
>>>>>>> confirmation
>>>>>>> on this? Does it add an additional filter or overwrite the existing 
>>>>>>> filter
>>>>>>> you set?
>>>>>>>
>>>>>>> Thank you.
>>>>>>> Sincerely,
>>>>>>> Hriday.
>>>>>>>
>>>>>>> On Tue, 8 Dec 2020 at 16:19, Jakob Erdmann <[email protected]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hello,
>>>>>>>> the ssm device currently does not expose the conflict-related
>>>>>>>> vehicles. Hower you could use
>>>>>>>>
>>>>>>>> addSubscriptionFilterFieldOfVision to get all vehicles within a
>>>>>>>> given range and angle
>>>>>>>> or
>>>>>>>> addSubscriptionFilterTurn which returns foe vehicles on and
>>>>>>>> approaching upcoming junctions along the route of the ego vehicle.
>>>>>>>>
>>>>>>>> regards,
>>>>>>>> Jakob
>>>>>>>>
>>>>>>>> Am Di., 8. Dez. 2020 um 14:03 Uhr schrieb Hriday Sanghvi <
>>>>>>>> [email protected]>:
>>>>>>>>
>>>>>>>>> Hello,
>>>>>>>>>
>>>>>>>>> I am a 2nd year PhD student at Trinity College Dublin, but I am
>>>>>>>>> new here.
>>>>>>>>>
>>>>>>>>> I am trying to set a range on vehicles such that they detect the
>>>>>>>>> presence of any vehicle "X" metres in front of them. I am currently 
>>>>>>>>> using a
>>>>>>>>> context subscription on each vehicle with a LaneFilter applied, 
>>>>>>>>> setting
>>>>>>>>> downstreamDist to a value. (
>>>>>>>>> https://sumo.dlr.de/daily/pydoc/traci._vehicle.html#VehicleDomain-addSubscriptionFilterLanes
>>>>>>>>> ). However, this does not seem to detect the vehicles "X" metres in a
>>>>>>>>> radial distance (
>>>>>>>>> https://sumo.dlr.de/docs/TraCI/Interfacing_TraCI_from_Python.html#context_subscription_filters
>>>>>>>>> ) in the case where the vehicles meet each other at the intersection 
>>>>>>>>> at a
>>>>>>>>> perpendicular angle.
>>>>>>>>>
>>>>>>>>> It seems that using an SSM device would be ideal in this case,
>>>>>>>>> since it lists out all the information I might require (
>>>>>>>>> https://sumo.dlr.de/docs/Simulation/Output/SSM_Device.html#encounter_types
>>>>>>>>> ). I am not able to figure out how to get this information dynamically
>>>>>>>>> though. Please advise.
>>>>>>>>>
>>>>>>>>> Thank you.
>>>>>>>>> Sincerely,
>>>>>>>>> Hriday
>>>>>>>>> _______________________________________________
>>>>>>>>> sumo-user mailing list
>>>>>>>>> [email protected]
>>>>>>>>> To unsubscribe from this list, visit
>>>>>>>>> https://www.eclipse.org/mailman/listinfo/sumo-user
>>>>>>>>>
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>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Hriday
>>>>>>> https://www.linkedin.com/in/hriday-sanghvi/
>>>>>>> _______________________________________________
>>>>>>> sumo-user mailing list
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>>>>>>> To unsubscribe from this list, visit
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>>>>>>>
>>>>>> _______________________________________________
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>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Hriday
>>>>> https://www.linkedin.com/in/hriday-sanghvi/
>>>>> _______________________________________________
>>>>> sumo-user mailing list
>>>>> [email protected]
>>>>> To unsubscribe from this list, visit
>>>>> https://www.eclipse.org/mailman/listinfo/sumo-user
>>>>>
>>>> _______________________________________________
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>>>
>>>
>>> --
>>> Hriday
>>> https://www.linkedin.com/in/hriday-sanghvi/
>>> _______________________________________________
>>> sumo-user mailing list
>>> [email protected]
>>> To unsubscribe from this list, visit
>>> https://www.eclipse.org/mailman/listinfo/sumo-user
>>>
>> _______________________________________________
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>
>
> --
> Hriday
> https://www.linkedin.com/in/hriday-sanghvi/
> _______________________________________________
> sumo-user mailing list
> [email protected]
> To unsubscribe from this list, visit
> https://www.eclipse.org/mailman/listinfo/sumo-user
>
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