An 'absolute minimum' value is a design paremeter used when there is an existing constraint on a proposed or existing cycle facility.
For instance, an 'absolute minimum' width of a one-way cycleway is 1.5m for a short section where there is a physical constraint.
'Absolute minimum' values should be contrasted with 'Desirable minimum' values, used when there is no physical constraint.
For Highways England schemes, designers have to record the reasons why they have had to use an absolute minimum, rather than a desirable minimum.