Why does a highway unit's placement depend on the closure?
The lane closure decides where a unit can stand, how the crew gets to it and how the servicing truck reaches it. A placement that is safe on one day can be unsafe on the next when the closure moves, so the spot is set each day from the plan.
A closure fences off a lane or a shoulder, and the space inside the fence is the only space a unit can use. The unit is placed inside it, and clear of the barrier so that a crew member can walk around it.
The sight line matters as much as the space. A unit that blocks a driver's view of the crew or of a sign is a hazard, so the placement is checked from the traffic's point of view as well as the crew's.
A closure that changes overnight moves the safe spot. The crew checks the unit's position at the start of each shift and moves it if the new closure requires.
How are units anchored against the wind and the traffic?
A unit on a closed lane or shoulder is anchored against the wind and the air pressure from passing trucks, and its door is checked for a loose hinge. A unit that moves in traffic is moved back before anyone uses it again.
A passing truck pushes a wall of air ahead of it, and a light unit can be pushed or tipped. The anchor is set to the ground and the unit is checked after each heavy truck passes close by.
Wind on an open bridge deck or a raised span is stronger than at ground level. The units on the span are anchored with a heavier base and checked more often.
The door is the first part to fail under pressure. Its hinges and latch are checked at each visit, and a door that will not latch is repaired before the unit is used.
How does servicing fit inside a closure window?
Servicing is booked inside the closure window, so that the truck can reach the unit safely and the crew is not working inside the live traffic. A window that is missed is rebooked with the site manager on the next closure.
The servicing truck needs the same closure as the crew to reach the unit. A window is booked in advance, and the route for the truck is walked before the window opens.
A unit used heavily by a crew on a long shift is pumped at the end of the shift, not at the start, so the next crew finds it clean. The window is set to match the crew's finish.
A missed window is not left as a missed visit. The record shows the gap, and the site manager agrees a second window so the unit is serviced before the next shift.
What happens when the crew moves to the next span?
The unit is moved when the crew moves. The unit is pumped, lifted and set at the new point inside the next closure, and the crew does not go without a unit during the move.
The move is planned against the closure, and the new position is set before the old one is taken up. The crew confirms the new spot with the site manager on the day.
A unit that is lifted full is a hazard, so it is pumped before the move. The truck and the crew are both kept clear of the traffic while the unit is moved.
After the move the unit is leveled, anchored and checked, and the visit schedule is updated for the new spot.