Access to work areas is unsafe. The work area is unsafe without traffic control. The shoulders or roadside are too narrow. Visibility is too restricted. Construction or other work is under way or planned.
Traffic is too heavy or too close.
Vehicle runoff potential is too high. Terrain is too rugged or vegetation is too dense. There is no area available or appropriate for planting. Site conditions are unsuitable for your group's age level or experience. Frequency of litter pickup is too great for your group.