The San Pedro Bay Ports of Long Beach and Los Angeles are the two busiest container ports in the country, and combined they are among the top five ports in the world. One of the key attractions for shippers to San Pedro Bay is the excellent rail connections available to access the rest of the country. Projected cargo growth will require capacity improvements to Port rail yards and rail network infrastructure as well as the Class I railroad corridors. The Port is changing rapidly due to increased cargo flows, community pressures, new legislation governing transportation behavior, and new operating modes developed to deal with the freight volumes. Therefore, the two Ports are collaborating on a Rail Enhancement Program to provide an update to a previous Rail Master Plan. The primary purpose of this study is to reduce truck traffic with its associated congestion and emissions impacts and maximize use of rail. The Rail Enhancement Program (REP) considers projected cargo growth so that the impacts of increasing cargo volumes on the rail system are understood; and improvements can be analyzed, designed, evaluated and developed to address these impacts. Improvements include rail operations, rail yards and rail network infrastructure. The REP includes over forty individual projects. The steps of the REP development process include the following: 1) Conceptual design and capacity analysis of potential rail yard projects; 2) Scheduling of rail yard developments to meet demand considering environmental processes, design, contracting and construction requirements; 3) Simulation modeling of rail network operations to establish a 2005 Baseline, identify future deficiencies, and plan phased improvements; 4) Evaluation of rail yard and rail network improvement concepts based on feasibility and environmental impact metrics; and 5) Plan implementation (agency coordination, regulatory compliance, funding, and sustainability).