The 2020 Tokyo Olympics is expected to cause serious congestion at railway stations in the metropolitan area during morning rush hours, a Japanese researcher has warned.

Hub stations and those near game venues will be overcrowded unless Olympic-goers are diverted to less busy stations or measures are taken to have commuters avoid peak hours, Azuma Taguchi, a professor of traffic networks at the Faculty of Science and Engineering at Chuo University, pointed out in a recent study.

"There will be a need to promote staggered work hours or guide spectators to stations a little further from game venues," Taguchi said.

In the Tokyo metropolitan area, eight million people commute on around 47,000 trains operated per day. The Olympic events will draw an additional 650,000 people to the area on peak days, according to Taguchi.

Taguchi simulated the travel times and routes of commuters and spectators during commuting hours using government data to estimate congestion levels for stations and trains.

He predicted the number of trains with a congestion rate of 200 percent will increase by 50 percent. In the transport ministry's definition of congestion rates, 200 percent means passengers can barely read a magazine.

The number of people at major stations such as Tokyo and Shinjuku at any given time during morning rush hours will more than double, he estimated.

"Train operations could be disrupted if Olympic visitors who are not used to rail travel block the flow of people at stations which are already crammed," said Taguchi.

In the Tokyo Bay area where Olympic venues are concentrated, limited availability of train services could result in stations being flooded with more passengers than they can handle.

The number of passengers using the Yurikamome unmanned train system and the Rinkai Line run by Tokyo Waterfront Area Rapid Transit is expected to more than double at the time of the event, according to the study.

Given the difficulty of expanding train service capacity or changing game schedules, promoting telework is the only viable option to reduce the number of commuters during rush hours, Taguchi said.

He added congestion at train stations could also be significantly eased if Olympic visitors are guided to get off trains before reaching the closest stations to the venues and walk a longer distance.

"Efforts are needed to encourage visitors (to get off early and walk longer) by holding entertaining events on the way to the venues, for instance," he said.