Well heres a simple edit to emphazise the look of speed.



Comments very welcome.

Paul

think about this....if the plane is blurred and the background is still, you will show motion, or,....you can have the plane blurred and the background sharp, you can still show an effect of motion, but with both blurred, its a bit harder to see motion unless you are panning with a very slow shutterspeed ..........
........I have done lots of photography and understand the principles needed, to show the perspective you intend to display..........

Here is the first without any edit, then the two different ways to show motion.........

Yrs of practice with Photoshop..........

I wish I had thought of that explanation, but it won't quite work as precisely as I would like anyway, so I figured better not to say anything for fear of running out of space with all the steps I used.....
BTW, I never used " grow" at all.......just multiple and additive selections using " shift " with the "Magic Wand" and free selection tools with re-setting of the tolerance values along the way....then, inverting the selection and contracting the selection by a pixel and re-inverting before copying to a new layer for each image effect,........
Blurring was done with the A/C image re-selected and the motion blurr was used to create the motion effect allowing the new image to overlay the background on one and on the other the blurr was done to the background itself without the A/C being selected........next, I hid one of the three layers and saved it as a different image from the original, with the two different image effects saved as unique files......
After this, I took the three images and re-assembled them on a new canvas with enough space to insert a single pixel "stroke" in white to give a border and divider between and around each pic.............simple, eh ?

Not  quite a simple wand/grow/blur effect...........