Łódź HSR tunnel: 4,000-tonne TBM assembly pushes 2027 boring date

A 450-tonne gantry crane has lowered the cutterhead of a 4,000-tonne tunnel boring machine into the launch chamber at Retkinia in Łódź, positioning the heaviest single component of the machine to within ±5 mm and moving Poland's flagship high-speed rail project closer to boring operations scheduled to begin in 2027.

The machine is a Variable Density TBM, a type selected for ground conditions that shift between soft and water-bearing soils. It measures roughly 130 m in length and bores a tunnel of approximately 14 m in diameter — wide enough, by comparison, to accommodate a full-length main line railway tunnel bore housing twin tracks and overhead clearance for 25 kV electrification of the kind used on high-speed lines. Several major components are already installed underground at the Retkinia site. Further assembly and testing will follow before the cutterhead turns.

Where will the tunnel run?

The bored section will run from Retkinia to Łódź Fabryczna station, forming part of railway line No. 85. That line, in turn, is one element of the planned high-speed "Y" — the trunk corridor intended to link Warsaw and the new central airport with Łódź, Wrocław and Poznań.

The design parameters are those of a genuine high-speed railway, not a conventional main line upgraded for faster service. Infrastructure is being designed for speeds of up to 350 km/h, with regular passenger operations planned at up to 320 km/h — a service speed in the same bracket as France's TGV network. Inside the Łódź tunnel itself, the ceiling is lower: trains will run at no more than 160 km/h, a figure consistent with the alignment's urban constraints.

The gap between design speed and operating speed deserves attention. A 350 km/h design specification does not guarantee 320 km/h service; certification, rolling stock capability and signalling all sit between the two. Polish infrastructure managers have yet to publish the certification regime for the corridor.

What does the construction timeline look like?

Main construction of the tunnel is scheduled for completion in 2029, to be followed by testing and certification. No opening date for passenger services is given in the project material, and readers should treat 2029 as a construction milestone rather than a service launch.

The logistics plan contains one of the more concrete claims in the announcement. Port Polska estimates that transporting excavated material by pipeline rather than by road will eliminate around 80,000 heavy goods vehicle journeys during construction. That figure is an estimate, not a measured result — the pipeline is untested at this scale in this corridor — but if it holds, it removes a volume of HGV traffic comparable to more than 200 lorry movements per day across a multi-year construction period.

What has been verified, and what has not?

The physical progress is verifiable: the cutterhead is underground, positioned to a stated tolerance, and the TBM's major components are being installed in the launch chamber. The claims that follow — the 2027 boring start, the 2029 construction completion, the 80,000-journey saving — are projections from the project parties, each subject to the ordinary risks of large tunnel works: ground conditions, machine reliability and commissioning schedules.

What the announcement does not say is equally relevant. There is no published cost update for the bored section, no date for the start of testing, and no confirmation of which sections of the wider Y will be ready to connect to the tunnel when it is complete.

The next verifiable milestone will be the start of boring itself, expected in 2027.