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Re: [sumo-user] Understanding SpeedDev.
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No. SpeedFactor is selected randomly at vehicle creation based on speedDev and remains constant over the vehicle lifetime (unless changed via traci or type calibrator). The speedFactor distribution thus applies to the fleet as a whole.
Hello,
I asked this question a while ago but looking at it again, I was still confused if I'm understanding this correctly.
Let's assume the following to determine a single vehicle's speed.
Lane speed limit = 30 m/s
Speed Factor = 1.0
Speed Dev. = 0.1
First, the lane speed limit (30m/s) is multiplied by the speed factor (1.0).
And following the distribution and the speed dev (0.1), ~68% of the time, the vehicle will drive between 27m/s and 33m/s, ~95% of the time, the vehicle will drive 24m/s and 36m/s.
This determines the vehicle's desired speed.
Finally, the vehicle speed is min(maxSpeed, desired speed) where maxSpeed is defined in the .rou file.
Could you please confirm if this is the right understanding?
Thank you!
- It seems like the max speed is defined as 'the maximum speed desired by driver under any circumstances' according to https://sumo.dlr.de/docs/Simulation/VehicleSpeed.html.
Then is desired speed = maxSpeed? Also, is the desired speed calculated by the multiplier factor (from the distribution in which speed factor is the mean and speed dev is the standard deviation) * lane (or edge) speed limit?
- Doesn't the formula you provided (speedFactor * speedLimit) describe how 'desired speed' is calculated? If maxSpeed can be thought as the desired speed (assuming that my thoughts on #1 is correct), what does it mean that maxSpeed can override the desired
speed?
- A follow up question is the SUMO vehicle definition says that the default value of maxSpeed is 55.55 m/s. If maxSpeed can override speedFactor
* speedLimit, wouldn't the vehicle always drive at 55.55m/s?
Sorry if my questions are unclear. Please let me know if there is anything I can further clarify.
Thank you very much for your replies.
1) the distribution assigns a factor to each vehicle by default this is in the range [0.2, 2]. This is multiplied with the speedLimit to compute the desired speed on a given road
2) maxSpeed can override the value of speedFactor * speedLimit
Thank you for your explanation.
- So the speed determined through this distribution, is that the maxSpeed of the vehicle? For example, if the distribution assigns 29m/s to a vehicle, would that be the maxSpeed of the vehicle?
- If the maxSpeed is the hard limit on the speed, does that mean it can override the lane (or edge) max speed?
Thank you,
the distribution of speeds will have their mean at 30m/s and will be (almost) normally distributed with a standard deviation of 0.1 * 30 = 3m/s.
This means ~68% drive between 27ms/ and 33ms but 95% will be found between 24m/s and 36m/s.
It's "almost" normal because sumo caps the normal distribution at configurable thresholds. By default 100% will drive between [0.2 * 30m/s and 2 * 30m/s] but you can also configure these thresholds.
Also, the maxSpeed of the vType is a hard limit.
Hello,
I'm having a trouble with understanding the explanation on how speedFactor and speed deviation work.
If I'm using the default values of speed factor (1) and speed dev (0.1), how do they affect the vehicle speed on the lane with maximum speed of 30m/s?
Does this mean that the vehicle will drive in the range between 27m/s to 33m/s (or 30m/s since the max speed is capped at 30m/s)?
And would that be because the lane-assigned speed (30m/s) is multiplied by the speed factor of 1 with deviation of 0.1?
Thank you,
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