Zipcar Inc., the Cambridge-based vehicle-sharing service, announced plans Tuesday to expand its Zipvan cargo service across all its North American markets.

Zipvan started in London and now accounts for more than 10 percent of Zipcar’s UK operations, the company said. Zipcar, which rents vehicles by the hour, tested the program in the San Francisco market, starting last year. In the spring, it began offering the service in the Boston and Washington, D.C., markets, with rates starting at $15.75 per hour and $109 per day.

In recent months, the program was also made available in Zipcar’s Chicago and Toronto markets.

In a press release, the company said that it is launching the service Tuesday in Seattle, Los Angeles, Philadelphia, and Portland, Ore. It also said that it plans to roll out the service to its remaining metro markets in North America over the next 12 months.

The Zipvan service is designed for such tasks as shopping trips involving large items or moving from one apartment to another. Business customers can use the service to make deliveries, the company said.