Bed size?

If you use the no-dig system then the theory is that the compost you put over the top and the undisturbed soil underneath is less affected by compaction when stood on so bed width in theory becomes less of an issue. Personal experience: my beds have been established for quite some time and are in good nick so I don't worry about standing on them on occasion to make life easier and I do sometimes actually tread in the brassica beds to give the plants a firmer hold. Not sure how this would go with claggy clay underneath though.