The Zephyrette was a tri-weekly train consisting of a Budd Rail Diesel Car (RDC) run by the Western Pacific Railroad between Oakland, California, and Salt Lake City from 1950 to 1960.

Both the existence and western terminus of the route were shaped by the stipulations of regulatory agencies, while the two RDCs the railroad purchased for the train were substantially modified before entering revenue service.

The Zephyrette RDCs achieved considerable cost savings over their conventional predecessor and steam locomotives running similar routes, as well as operational advantages related to their quick acceleration and high cruising speeds.

[4] Ultimately, the ICC granted the Western Pacific's request to discontinue its daily Royal Gorge service with the condition that it be replaced by a route between Oakland and Salt Lake City that operated three times a week.

[3] In January 1950, the Western Pacific conducted a ten-day evaluation with a Budd RDC-1 demonstrator in revenue service between Portola, California, and Salt Lake City, a distance of 600 miles (970 km).

However, the California Public Utilities Commission stipulated that the new service must extend to Oakland, meaning that the total one-way distance to Salt Lake City would be 924 miles (1,487 km).

[8] The Western Pacific's Zephyrette consisted of a Budd RDC that was powered by twin inline six General Motors diesel engines, which each produced 275 horsepower (205 kW), and equipped with Allison torque converters.

[11] The service operated on a tri-weekly schedule, with eastbound trains departing Oakland at 7:57 pm every Sunday, Wednesday, and Friday, and their westbound counterparts leaving Salt Lake City at 7:30 am on the same days.

They also provided numerous advantages over conventional consists, especially in terms of their ability to accelerate quickly and maintain high sustained speeds, which allowed for faster service of the route's conditional stops than had previously been possible.