The San Diego Metropolitan Transit System in the US has placed a $205m order with German firm Siemens for 57 S70 type light rail vehicles.
The 81ft-long vehicles have the capacity for 60 people and will replace part of the agency's existing 134-car fleet on the network's blue and orange lines.
The contract forms the first phase of a major overhaul of the two lines, funded using economic stimulus funds under the American Recovery and Reinvestment Act.
Delivery of the new vehicles will begin in 2011.
Siemens is the sole provider of light rail cars for the transit agency, which operates an 83km track network in the city.