The I-15 Commuter Rail Feasibility Study evaluated the potential of conventional commuter rail services between two corridors: Temecula North and Temecula South. Apart from the evaluation of conventional commuter rail options, this study also explored the potential of implementing a commuter rail level of service on the proposed California High-Speed Rail (HSR) system between Temecula and San Diego.

Corridors evaluated included:

• Temecula-Corona: between Temecula and points west (via Corona), including Los Angeles and Orange County work centers; and between Temecula and points east (via La Sierra), including Riverside and San Bernardino.
• Temecula to San Diego: Commuter Rail
• Temecula to San Diego: High Speed Rail

The evaluation of commuter rail options required the development of forecasts for ridership, revenue and costs, as well as assessment of potential mobility improvements and institutional issues. The planning year for the study was 2030.

This analysis utilized the same evaluation criteria developed for the 2005 RCTC commuter rail study. Feasibility was determined by examining ridership in 2030, passenger trips per train, fare box recovery ratio, right-of-way issues, daily trip time savings, access to low income households, operating cost per passenger-mile, total capital costs and capital costs per passenger.

Top four ranking alternatives:

• Alternative A: commuter rail service between Temecula and both Los Angeles and Laguna Niguel
• Alternative C: commuter rail service between Lake Elsinore and both Los Angeles and Laguna Niguel
• Alterative C1: a variant of Alternative C, assume both a Dos Lagos station and a public-private partnership partially covering public costs of implementing commuter rail station
• Alternative G: commuter rail between Temecula and downtown San Diego, along the alignment identified for the proposed California High-Speed Rail Service

Alternative G, with commuter rail service from Temecula to San Diego, does the best in terms of passenger trips, passenger trips per train, fare box recovery, access from low income households, and operating costs per passenger-mile. However, its implementation cost of $1 billion is three times that of the next highest, Alternative A.

The analysis supports public-private partnerships, where private developers help fund or donate right of way and contribute to the overall capital costs. This concept could reduce implementation costs for Alterative C1 by $113.2 million—assuming that developers provide or fund the right-of-way requirements, the stations, and contribute $50 million in rolling stock requirements. This approach would make the service more cost efficient and could increase the viability of the project.

High-Speed Rail, if implemented, would need to address the major commuter demand from Temecula with commuter focused schedules going south.