Alternatives to Light Rail Stages 1 and 2A were examined in the 2024 report 21st Century Public Transport Solutions for Canberra. At that time, the cost of Stage 2B was estimated at around $4 billion. DRA Vice President Dr John Bell, a co-author of the report, has since revisited those estimates.

Working with colleagues who have relevant engineering and infrastructure experience, the co-authors estimated the likely cost of Stage 2B by scaling up the per-metre construction costs of Stage 1 and adding allowances for major additional works such as bridges, culverts, utility relocations and other services. In several locations, existing bridges would need to be demolished and replaced. Estimates for new bridge construction were based on the costs of recently completed comparable structures. Additional allowances were also made for the engineering complexities associated with routing light rail around Parliament House and down Adelaide Avenue. The estimates included the cost of modifying trams to operate on batteries, as well as construction of the Woden tram/bus interchange.

Subsequent design changes have only increased the likely cost. For example, the proposed cut-and-cover tunnel from Commonwealth Avenue to State Circle alone could add more than $50 million and plus modification to bridges over Federation Mall. Even in 2024 there was considerable uncertainty about how costs would evolve over time. Since then, many construction costs have risen by more than 20 per cent.

Taking these changes into account, the likely cost of Stage 2B is now estimated to be around $5 billion. With the cost of Stage 2A already approaching $900 million, and likely to reach around $1 billion by completion, the combined cost of Stage 2A and 2B could therefore approach $6 billion.
The original 2024 report by Leon Arundell, John Bell, Kent Fitch, Russ Morison, Mike Quirk and Anthony Senti is available at 21st Century Public Transport Solutions for Canberra.