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[sumo-user] Secure gap, brake gap and stopping distance


Is there a difference between secure gap, brake gap and stopping distance (from kinematics)?

As farĀ as I understand, the secure gap / brake gap / stopping distance calculation does not depend on the CF model, since this calculation is the same for all CF models. My CF model is Krauss.

1. My assumption was that the secure gap and brake gap are the same. But when I check on "show brake gap" in the SUMO-GUI, and display the "secureGap" using traci.getSecureGap(self, vehID, speed, leaderSpeed, leaderMaxDecel, leaderID=''), the values do not seem to reflect what happens in the GUI - for example, when TraCI outputs a secureGap of 0.0 - there is still a line sized bigger than 0.0 shown in the GUI.
- What would I set as the leader speed if there is no leader in front of it - the max speed on the lane (13.89 m/s)?

2. If I assume that the secure gap and brake gap are the same as the stopping distance used in kinematic physics, then does it just use those equations to calculate this stopping distance value? That is, using (Final velocity)^2 - (Initial velocity)^2 = 2 * acceleration * Distance to calculate the Distance for a constant acceleration / deceleration?

3. On a side note, what is the significance of emergencyDecel variable used in SUMO - to put it differently, why is just one deceleration capability value not enough? - since I couldn't find an equivalent to that in real-world driving.

Thank you.


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