Cost basis
The new-build tram elements of this proposal are costed against outturn figures from recent British light rail construction rather than against scheme-specific estimates. This section sets out those benchmarks and the basis on which they are applied.
The same benchmarks are used throughout the document and in the companion analysis. Costs are standardised to 2025/26 prices using the ONS Construction Output Price Index, so that projects delivered in different years can be compared on a common basis.
Benchmark projects
Costs are drawn from a report compiled on behalf of Edinburgh Council combined with Greater Manchester Combined Authority minutes, and are standardised to 2025/26 prices using the ONS Construction Output Price Index.
Table 4.1: Light rail construction benchmarks, standardised to 2025/26 prices
The Trafford Park extension is dated 2017 in the Edinburgh Council source, though it opened to the public in 2020. The Second City Crossing figure derives from a project cost of £165m for a 0.8 mile, 1.29km section.
Applying the benchmarks
The spread across these projects is wide, and the reason is instructive. The Manchester Metrolink Second City Crossing cost roughly double even relatively expensive suburban extensions such as Trafford Park, because it is a city centre route carving through historic streets, with the heritage constraints and utility diversions that follow. Suburban and radial alignments running through lower-density urban fabric behave more like Trafford Park.
Two benchmarks are therefore applied in this document.
£291.10m
Per mile for the L1 city centre spine, benchmarked against the Second City Crossing as the closest available comparator for a route of that character.
£143.68m
Per mile for the Seacroft, Belle Isle and Roundhay alignments, benchmarked against the Trafford Park extension.
Station costing
Station upgrades are costed against Network Rail Category D hub station design guidance, which puts the base cost at £2.46m per station. This is doubled to £4.92m for Phase 1 upgrades, the doubling treated as the buffer for optimism bias and unforeseen scope variation on top of amenity and public realm works.
New stations on existing alignments are costed at £30m to £40m including a 30% contingency, a level that should be revisited against current outturn figures during detailed design. The figure applied in this document is £32.5m per new station.
Electrification benchmark
Electrification is costed against the RIA Electrification Cost Challenge, published in March 2019 and subsequently cited by the House of Commons Transport Committee. The RIA finding is that a simple electrification project should cost between £0.75m and £1m per single track kilometre, and that a complex project should not normally exceed £1.5m per stkm. These are the rates a competently delivered scheme should achieve, evidenced against UK and international outturn including the Danish and Ulm to Lindau programmes, rather than the rates seen on the Great Western Electrification Programme.
The RIA rates are expressed in 2019 prices. They are normalised here to 2025/26 prices using the ONS Construction Output Price Index for all new work, applying a factor of 1.35, which is the same index basis used to standardise the light rail benchmarks in table 4.1.
Table 4.2: RIA Electrification Cost Challenge benchmarks, normalised to 2025/26 prices
This proposal applies the complex project ceiling of £2.03m per single track kilometre to all three corridors requiring electrification, with a 30% margin applied on top. All three involve Victorian structures, restricted clearances or complex junction layouts, and continuous wiring brings those features into scope.