Japan's transport ministry says a large-scale test conducted earlier this week, aimed at easing traffic on Tokyo's Metropolitan Expressway during next year's Olympics and Paralympics, failed to achieve a goal that had been set.
People are concerned that traffic congestion on the expressway will be heavy during the Summer Games if no measures are undertaken.
The Tokyo Metropolitan Government, the organizing committee of the 2020 Games, and other bodies held the test on Wednesday.
The authorities closed many entry points for lanes bound for central Tokyo. They were hoping to cut traffic by up to 30 percent. But the transport ministry says congestion fell only 7 percent.
The officials also wanted to achieve a travel time of 20 minutes or less on a section of the expressway between the athletes' village and the New National Stadium. But it took about 24 minutes to cover the route.
The stadium will serve as the venue for some events, as well as for the opening and closing ceremonies of the Games.
A similar test will be conducted on Friday.