Construction methods · Heavy lift, moving and accelerated construction

Working over live railways: possessions and blockades

Anything over a live railway is built inside possessions: short overnight closures of a few hours, or planned blockades of a weekend. The method is planning: everything is prepared, every lift is rehearsed, and the possession is used only for what cannot be done with trains running.

How bridges get built · Heavy lift, moving and accelerated construction · Working over live railways: possessions and blockades

Also called: railway possession, track blockade, working within possessions

How it is done

Agree possession windows a year or more ahead; design the works so that only the lifts over the track need a possession.
Prepare everything outside: piers set back from the track, girders staged, cranes positioned, protection screens ready.
In the possession, isolate the overhead line, lift and connect, install protection, hand back on time; a late hand-back costs more than the works.

Where it fits

All bridges over operating railways; overhead line electrified routes need extra isolation time.

Where it does not

Any method that needs falsework or work over the track outside possessions; crane operations that could foul the track.

Plant, pace and money

PlantCranes positioned outside the boundary, protection screens, isolation equipment.

ProductivitySet by the possession calendar, not the crane.

CostPossession charges and penalties dominate; the game's railway sites carry a possession factor in the schedule.

Risks and controls

What goes wrong

Overrun of the possession, crane collapse onto the track, dropped objects, electrocution.

Quality assurance

Possession planning with method statements and rehearsals, safe systems of work with the railway, exclusion zones.

Examples

UK Network Rail Christmas blockades, Korean KORAIL night possessions, Japanese Shinkansen overbridges (rotation and slide methods).