# Thread: Video of Car Driving By Camera, How Fast is it Going?

1. Hi,

I'm curious to know, based on the video below, if anyone can conclusively say how fast the car driving by is going? Would you need additional information?

Video of Car Driving By Camera, How Fast is it Going?

Here's the infographic, is this enough to solve how fast this car is going (in mph)?
http://cl.ly/PqpJ

2.

3. It took about 1 second to travel what looks like about 50 feet so with that information you could tell but the exact distance isn't known so there could be a little difference.

4. Originally Posted by cosmictraveler
It took about 1 second to travel what looks like about 50 feet so with that information you could tell but the exact distance isn't known so there could be a little difference.
So maybe if I got exact distance traveled, and determined how many frames it took for the car to travel that distance... would that be enough?

5. Unless you know the frame rate of the camera you can't tell the time in a film accurately - i.e. what is shown may not be in synch with reality.
Are we getting into conspiracy theory here?
FBI assassinations?

6. Originally Posted by Dywyddyr
Unless you know the frame rate of the camera you can't tell the time in a film accurately - i.e. what is shown may not be in synch with reality.
Are we getting into conspiracy theory here?
FBI assassinations?
Heh, I'm just curious to know how fast he was driving, and if determined, can determine the speed at which the tree was hit, based on car-to-tree damage. I'm trying to understand what speed he may have hit the tree at. If the speed determined by the camera here is XXmph, and based on past car accidents where certain amount of tree damage was done to the vehicle based on an equivalent speed... that's what I'm trying to understand. It's just piqued my interest is all.

7. Originally Posted by Dywyddyr
Unless you know the frame rate of the camera you can't tell the time in a film accurately - i.e. what is shown may not be in synch with reality.
If I found out what the framerate that camera is filming out (more than likely 30fps), then that would establish a good reference.

8. The biggest problem here is that the car RAN THE RED LIGHT!!

9. Originally Posted by cosmictraveler
The biggest problem here is that the car RAN THE RED LIGHT!!
indeed he did Im going to drive down there and measure distance. The camera was filming at 30fps.

10. Oops: addendum - then you'd also have to check/verify that the playback is done at that speed.
(I don't know much about filming/ video, so I don't know* if it's possible to play back at a different speed than it was recorded).

* Although I'd be surprised if it wasn't.

You don't need to measure on-site though.
If you know the car make/ model then you can use the known length of the vehicle to get distances covered (how long to traverse its own length for example) - that obviates any problems with establishing other data points.

11. if he knows the frame rate he wouldn't have to worry about playback speed as he would just count how many frames it took for hte car to travel the distance. If one frame represents 1 second for instance(which would look really choppy) then he would just count each frame as one second of time. but in this case of 30fps. then he would have to count the frames and divide by 30 to get the number of seconds to go the distance he has determined, such as car length or distance from corner to street light or whatever.

12.

13. Originally Posted by seagypsy
if he knows the frame rate he wouldn't have to worry about playback speed as he would just count how many frames it took for hte car to travel the distance. If one frame represents 1 second for instance(which would look really choppy) then he would just count each frame as one second of time. but in this case of 30fps. then he would have to count the frames and divide by 30 to get the number of seconds to go the distance he has determined, such as car length or distance from corner to street light or whatever.
But surely to do that you need a copy of the film itself to examine it frame by frame?

14. Car is 2013 Mercedes C250.
Length Dimensions: 180.8 inches (15.07 feet)

I'll download the video tomorrow, count frames, and post an infographic with length of overall distance traveled.

15. added infographic with precise frame count, car dimensions, path traveled in milliseconds.

Here's photo:
hastings-infographic.png

Here's raw data:

Video Framerate = 30fps.
Frame Count from Entry to Exit = 19 Frames
Time of Travel = 630ms

Car Dimensions = 180.7 inches (15.6 feet)
Distance of Travel = 903.5 inches (75.3 feet)

Therefore, the car approximately traveled 903.5 inches in roughly 630 milliseconds.