[sumo-user] Computing headways at intersections

[Daniel Aguilar Marsillach <daniel.aguilarmarsillach@xxxxxx>]

Hi there, 

I'm having an issue with headway and lead vehicle identification using Traci when a lead vehicle enters a junction. The subscribed headway between two vehicles is 0m, but the physical distance is 79.00m. Is this expected? Are there any junction parameters or settings that I may be misusing? I'd appreciate suggestions on how to get the correct headway directly from SUMO/Traci before implementing a correction in the Python API.

Scenario:  

The vehicle follower_1 is moving from east to west and is approaching the junction. I have circled it in yellow.  The vehicle leader_0 is moving from south to north, has just crossed the yield line and is turning left, I have circled it in red.  Both are IDM controlled vehicles and default sumo safety checks are enabled. 

 The subscribed Traci variables are:  

 [tc.VAR_LANE_INDEX, tc.VAR_LANEPOSITION, tc.VAR_ROAD_ID, tc.VAR_SPEED, tc.VAR_SPEED_LAT,
                          tc.VAR_EDGES, tc.VAR_POSITION, tc.VAR_ANGLE, tc.VAR_SPEED_WITHOUT_TRACI,
                          tc.VAR_FUELCONSUMPTION, tc.VAR_DISTANCE, tc.VAR_LANEPOSITION_LAT, tc.VAR_ACCELERATION,
                          tc.VAR_WAITING_TIME, tc.VAR_LANE_ID, tc.VAR_NEXT_LINKS]

Traci Subscription Results for follower_1: 

{82: 0, 86: 39.89055103780684, 80: '2', 64: 12.819908744019667, 50: 0.0, 84: ('2', '5'), 66: (80.10944896219317, 1.6), 67: 270.0, 177: 12.819908744019667, 101: 1346.3627500766254, 132: 34.790551037806836, 184: 0.0, 114: 0.5894244551240924, 122: 0.0, 81: '2_0', 51: (('5_0', False, False, True, ':junc_4_0', 'm', 's', 14.4),), 104: ('leader_0', 0.0)}

Traci Subscription Results for leader_0:

 

{82: 0, 86: 0.026256706772315397, 80: ':junc_8', 64: 3.0363730309804664, 50: 0.0, 84: ('0', '5'), 66: (1.5962922005461444, -7.174045403823011), 67: 359.95750918840696, 177: 3.0363730309804664, 101: 1104.0259317847099, 132: 92.82625670677231, 184: 0.0, 114: 1.463278654968172, 122: 0.0, 81: ':junc_8_0', 51: (), 104: ('leader_4', 27.97479278915113)}

Note that 104 in the dictionary above is VAR_LEADER and for follower_1 this value = 0m and that 51 is VAR_NEXT_LINKS.

I understand that leader_0 is the lead vehicle for follower_1 as it is the first vehicle to enter the intersection is on a link that overlaps with follower_1's route. I also replicated this in another map scenario using different .net.xml file and observed the same problem.

Best,

Daniel

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