https://www.whatdotheyknow.com/request/was_a_consultation_of_local_resi#incoming-3356842

Using the above link you'll be able to view the response and linked document with full reply and details.

From this I can see that the parish council did knowingly authorise on the basis that they knew low clearance vehicles would not be able to traverse this hump and despite reaching out to various representative groups have no record of review from anyone but the Oxford bus company who did initially object and a farmer who needed his equipment to pass through the village. 

There's no warning that some vehicles are known to be unable to use this road, therefore they knowingly created a hazard.