Case Study: California High-Speed Rail Authority achieves major cost, tunneling and environmental-impact reductions with Trimble Quantm

Reducing Costs While Minimizing Environmental Impacts

Trimble’s Quantm system was used by the California High‑Speed Rail Authority and Parsons Brinckerhoff to resolve difficult alignment choices through the Diablo and Tehachapi mountain crossings. The challenge was screening and refining millions of possible horizontal and vertical alignments under tight physical and environmental constraints to minimize infrastructure impacts, tunneling and overall capital cost—work that previous studies could not comprehensively evaluate.

Using Quantm, the team evaluated millions of alignments over three weeks to refine corridors and identify lower‑impact, lower‑cost options. Results included dramatic tunnel length reductions (e.g., I‑5/Grapevine from 28–35 miles to 18 miles; Diablo Range total tunneling down from 31 to 11.3 miles and single tunnels near 5 miles), localized tunnel cuts in Soledad and Lancaster, and estimated construction savings of up to $2–2.8 billion. The study accelerated an eight‑month task into three weeks, delivered actionable alignment options that reduce environmental impacts and costs, and established a repeatable process for future project stages.

California High-Speed Rail Authority