I think the comment below from Andrew Rowbotham on the BBC website seems fairly sensible- speed bumps and hearses do not mix well!
How long till the outrage campaign spun up about the insult to our dead of sending them over speedbumps?
"Mr Robathan said the route would go through the village of Brize Norton, but would not go through the nearby town of Carterton, which had narrow roads with speed bumps "which are not very suitable for corteges"."