Hypothetical law change? Lorry on bike: lorry's fault. Bike on ped: bike's fault

So the car /hgv/lgv/bus that is the killer? Or the person in control it?

There isn't a "killer". And there isn't an analogy with the handgun debate either. A handgun has no practical purpose other than killing people, so it's reasonable to ban them, whereas motor traffic has obvious benefits as well as dangers.

Once more, for the slow of thinking: Choosing any of the options above, rather than walking or cycling, gives you the potential to cause a lot of damage. With that potential comes a responsibility not to do so.

by driving a car or HGV, you are using a tool that has the potential to easily kill someone else, and therefore your responsibility to avoid accidents is greater than if you are walking or cycling.
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There's nothing wrong with drivers being forced to take on more responsibility for keeping roads safe, as their choice of transport is responsible for making them dangerous in the first place.