RIO DE JANEIRO — With a half-million people set to descend on this traffic-choked megacity for the Olympics starting Friday, officials have yet to launch their main transit improvement: a $3 billion subway extension that cost two-thirds of Brazil’s transportation spending for the Games, The Wall Street Journal reported.

Rio’s state government said trains have been circulating to test Line 4 for weeks, but some experts say it could be different with thousands of passengers aboard. Despite a massive investment, the new subway ends 8 miles short of the Athletes' Village, so riders heading to Olympic venues will have to take a bus, according to the report.

The 10-mile railway, almost two decades in the making but seven months past its original completion date, is emblematic of Rio’s hectic preparations for the Olympics, which have also featured athlete’s quarters so unfinished that some teams moved out, according to the WSJ.

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