Traffic congestion is expected in central Seoul this weekend due to labor rallies and marathon events, police said Friday. The Korean Confederation of Trade Unions, a major umbrella labor union, plans to hold a preliminary rally near the Seoul Regional Employment and Labor Office in downtown Seoul at 1 p.m. on Saturday, according to the Seoul Metropolitan Police Agency. KCTU members will then march through downtown Seoul before holding their main rally for about an hour on the road between Sungn