Hello, the relationship between density and speed is a macroscopic property of traffic and I don't know a single microscopic model which uses density directly. Within a micro-simulation this relationship is induced by microscopic interactions between the vehicles. As far as my understanding goes, part of this is the interaction between vehicles of different speed and some other part may be due to feedback loops when drivers are braking stronger than absolutely needed. This latter part was discussed a while ago on the mailing list and some car-following model changes were proposed to increase the effect size. You can find a record of that discussion here: http://comments.gmane.org/gmane.science.simulation.sumo.user/5926 regards, Jakob
2014-10-19 0:36 GMT+02:00 Charalambos Menelaou < [email protected]>: > > On 10/19/2014 1:19:45 AM, Charalambos Menelaou < > [email protected]> wrote: > Hi, > > I understand that you had said me but, the idea is that in circle after > long time all vehicles their following the vehicle with the lowest speed. > > I believe that this is not correct since vehicles are not reduce their > speed because of density but because they can not overcome their leader. > > So, is any model where takes the density as parameter to declare the > vehicle speed? > > (I.P. As density increases the speed decreases.) > > Best regards. > > On 10/19/2014 12:25:07 AM, Michael Behrisch < > [email protected]> wrote: > Hi, > > Am 11.10.2014 um 16:59 schrieb Charalambos Menelaou: > > I was used two scenarios in 4km straight road lane > > 1. i was generate 2000 vehicles in 500 seconds 400 seconds 300 seconds > 200 seconds 100 seconds 50 seconds 25 seconds . > > 2.i was generate for 300 seconds 100 vehicles 200 vehicles 300 vehicles > 500 vehicles 750 vehicles 1000 vehicles 2000 vehicles 5000 vehicles 10000 > vehicles > > and i do not have the same results > > Without having vehicles of different speed or bottlenecks it won't be > possible to reproduce the fundamental diagram on a straight road. This > is due to the fact that the insertion procedure is somehow so > conservative that it will not induce enough distortion and after > insertion the distortions due to the dawdling are also small if all > vehicles have the same speed. In order to allow the small distortions to > "pile up" you have to drive in a circle for a long time. This is only an > abbreviated description, the theory behind the fundamental diagram is > much more involved and also still under heavy discussion, as far as I > know. But I hope you get the idea. > > Best regards, > Michael > > > ------------------------------------------------------------------------------ > Comprehensive Server Monitoring with Site24x7. > Monitor 10 servers for $9/Month. > Get alerted through email, SMS, voice calls or mobile push notifications. > Take corrective actions from your mobile device. > http://p.sf.net/sfu/Zoho > _______________________________________________ > sumo-user mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/sumo-user > ------------------------------------------------------------------------------ Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho _______________________________________________ sumo-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/sumo-user
