The Importance of motion blur and stabilisation in Onboard videos. 

Onboard videos are quite the pickle when it comes down to video quality. (granted this is just 1080p video upscaled to 4K)
Probably your best bet is to use correct ND filters with manual controls on your camera, however this video shows you not only the value of stabilisation and motion blur for speed perception but also shows that it can be done in post processing.
This perticular video (2nd one) was edited in AAE with Pixel motion blur effect.
Video: Gopro Hero 5 Black 1080p60 upscaled to 4K
Audio: Zoom h1n, auto + lo cut 80hz.
Stabilised with Demo version of Reelsteady GO (also wanted to test it out)