I'm sure the 2m amount was a political decision; after all, if 1m is good then 2m must be better, right?
The speed limit on motorways is 70. We all have accurate speedometers. Without average speed cameras or constant surveillance the effective speed limit is about 80, and quite a few do a lot more than that - and mostly get away with it.
2 metres, 6 feet, 1 metre, 3 feet it makes little difference. For starters it would need a bleeper to accurately monitor distances and sound a warning because most can't estimate distances sufficiently accurately. When it gets really busy it won't be obeyed, because it can't be. It's an inevitable fact of life.
A small number moving in the same direction at the same speed, no problem, until encountering others going the opposite way, but let's sidestep them. I want to go faster than you so an overtaking move is necessary. Wide pavement out of doors, still no problem, or shouldn't be. Restricted area in a supermarket, that ditherer in front, the temptation to push past 2 feet away is strong. Arrest that man?
Rushing to catch the train and the barrier or narrow entrance to the platform restricts the flow. You stand back, but others shuffle forward, 6 feet, 5 feet, 4 feet, 3 feet, who cares I just want to catch this train, 1 foot, we touch!!!! Arrest that man - and all the others?
Phew, got onto the platform without getting too close. Wasn't arrested. Others file on behind. Platform fills. 6 foot separation beomes 4, but that's about OK? Train arrives, some want to get off. Does everyone stand back? Do they ever, but maybe old habits will have changed!? We step onto the train and quickly (but some are not quick) decide whether it's better left or right, and others push behind. It's 30 minutes or an hour until the next train. Separation? It will evaporate. The train rapidly fills and all sit and stand close together. The train moves off, we're all trapped, no escape. Anyone who wants to get off again to avoid the scrum will make it worse - and create immediate danger of crushing. Arrest the whole trainload? How? Bar them from the train? Where do they go?
Either we stay locked down for possibly a year or more, or risk assessments are made so we know that travelling on public transport is riskier than by other means and plan accordingly.
My personal risk assessment for my local route today is that even as one in the higher risk categories I'd be safe to travel - because hardly anyone else is, 3 to a 2 car train. However, if normal peak hour loads returned I'd avoid them - like the plague they might carry! At least 95% of my rail journeys are non essential so the situation is academic and I'm not travelling.
The coronvirus hottest spots coincide with the densest populations. Like it or not a degree of herd immunity will be building up in those areas before vaccines and more effective treatments arrive. However the quicker identification of cases, better isolation when diagnosed, and better understanding of how best to treat sufferers should lessen the effects over time.
How to legislate both for the foolhardy risk takers and allow for those who are most risk averse is a massive challenge, especially when there are so many conflicting levels of vulnerabilty, many not obvious to any but the individual.
Have I the answer? The nation has to progressively take a few more risks and feel its way one step at a time. Personally, my immediate answer is to avoid public transport for several more months and take extra care. By September I hope to feel safe enough to be out and about a lot more. In the meantime I'm having to get used to Zoom meetings.
We have to get more people back to work as soon as it's reasonably safe to do so. The airlines (and probably cruise companies) are closing massive parts of their operations. If railways weren't as near to renationalisation as they seem to be they'd be going the same way.