TTC calculation

[whatgit]

Hello,

I am wondering how do you calculate the TTC in the dataset? I was assuming that
TTC = dhw/(xVelocity - precedingXVelocity); where TTC is time-to-collision, dhw is the distance headway, xVelocity is the ego vehicle's velocity, and precedingXVelocity is the preceding vehicle's velocity.

However, when I check it with the data, it was not correct. Therefore, I am wondering how do you calculate TTC in the dataset?

Please see the examples below.

Example from dataset_01

Case 1: vehicle id 2 is following vehicle id 13, here are the parameters in "track_data" of the vehicle id 2:

dhw = 112.62
ttc = -17.38
thw = 3.51
precedingXVelocity= -38.53
xVelocity = -32.06

If we follow the equation above. TTC should be equal to 112.62/(32.06-38.53) = 112.62/-6.47 = -17.40
(I think minus sign here indicate driving direction so I will ignore it for now)

Case 2: vehicle id 8 is following vehicle id 2, here are the parameters in "track_data" of the vehicle id 8:

thw = 2.29
dhw = 72.05
ttc = -104.67
precedingXVelocity = -32.04
xVelocity = -31.36

If we follow the equation above. TTC should be equal to 72.05/(31.36-32.04) = 72.05/-0.68 = -105.95

[Victorrsl]

Yes, I have found this problem too, may I ask if the proposer now knows the cause of this deviation?

[Victorrsl]

Hello,

I am wondering how do you calculate the TTC in the dataset? I was assuming that TTC = dhw/(xVelocity - precedingXVelocity); where TTC is time-to-collision, dhw is the distance headway, xVelocity is the ego vehicle's velocity, and precedingXVelocity is the preceding vehicle's velocity.

However, when I check it with the data, it was not correct. Therefore, I am wondering how do you calculate TTC in the dataset?

Please see the examples below.

Example from dataset_01

Case 1: vehicle id 2 is following vehicle id 13, here are the parameters in "track_data" of the vehicle id 2:

dhw = 112.62 ttc = -17.38 thw = 3.51 precedingXVelocity= -38.53 xVelocity = -32.06

If we follow the equation above. TTC should be equal to 112.62/(32.06-38.53) = 112.62/-6.47 = -17.40 (I think minus sign here indicate driving direction so I will ignore it for now)

Case 2: vehicle id 8 is following vehicle id 2, here are the parameters in "track_data" of the vehicle id 8:

thw = 2.29 dhw = 72.05 ttc = -104.67 precedingXVelocity = -32.04 xVelocity = -31.36

If we follow the equation above. TTC should be equal to 72.05/(31.36-32.04) = 72.05/-0.68 = -105.95

Hi, since TTC is the ratio of distance to speed difference, and this difference between two following vehicles generally fluctuates around zero, moments of zero speed difference are inevitable. How did the authors handle such cases? I analyzed the TTC values when the leading and following vehicles had equal speeds and found that the ratio of distance to TTC fluctuates between -0.009 and 0.009. This suggests that, during batch processing, the authors introduced a disturbance between -0.009 and 0.009 to the speed difference to prevent a zero denominator and ensure stability.