BLM road maintenance is done by what is called a travel management plan. The roads that have the most traffic or are within the more "visible" portions of each field office get the most attention.
It also makes a difference on what other constraints are in the area. For example if the area has some sort of wildlife restriction (nesting sage grouse or some raptor nest) it can not be bladed during that specific timing limitation.
Most field offices only have one individual doing road maitenance, and if they hit that particular road early, they may not get back to it before its conditions make it useless to blade.
(Just recently read a travel management plan that might upgrade a bunch of two tracks, making road hunting a lot easier)
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