London ? London subway workers walked out Saturday in a 24-hour strike timed to cripple the Underground during New Year’s Eve celebrations.

Guards and ticket office workers, upset over new staff assignments and schedules, began leaving their posts at noon, and the service was expected to slow down over the evening as others finished shifts and were not replaced.

London Underground said it hoped enough workers unaffiliated with the union behind the strike would turn up to keep some services running on all lines. About 4,000 of the 6,000 subway station workers belong to the RMT union.

Only 23 of the subway’s 275 stations were closed by late afternoon, and authorities said all lines had good service.