If everyone drove 100m apart on the motorway, the traffic would be even worse. Last time cars needed 100m to stop from 70 was when they used drum brakes all round.
If anyone ever gets prosecuted for driving to close to another, usually under driving without due care and attention, the guidelines in the Highway code are used,to determine correct distance, so yes maybe they are out of date, in your opinion, but they are what is used so you should obey them, otherwise technically in the spirit of them you are breaking the law.
Have always thought it just needs a very small tweak to set all gantry cameras to measure distance between vehicles and dish out 3 points, and say £200 fine to anyone driving to close, most people would sort out correct distances pretty soon after that.
Would be an awesome revenue earner to pay for NHS and road repairs etc