When physicist Tsuyoshi Hondou from Tohoku University in Sendai (Japan) realised how many people in his train carriage were using their mobiles at the same time, he decided to calculate how much of the electromagnetic radiation would escape through the windows and how much would bounce around the metal carriage. He also worked out how the latter would combine to cause exposures above the international safety limits. With regard to possible radiation danger from mobile phones and cell phone dangers, he concluded that, in a standard carriage seating 151 people, 30 people using their mobiles would definitely cause unsafe exposures, and that far fewer phones in use could have the same effect. Tsuyoshi is concerned that the dozens of new wireless gadgets coming on to the market will only make matters much worse.

Les Barclay, a radio engineering consultant who took part inthe UK Government's Stewart Enquiry into mobile phones and health risks, was cautious over Tsuyoshi's findings. While he conceded that microwaves will bounce around inside carriages and boost field levels, he suggested that the increase would be minimal because the power of the fields emitted by mobile telephones drops off exponentially (i.e. increasingly quickly) to virtually nothing a short distance away from each phone.

Tsuyoshi countered that the drop-off Les referred to would only occur if the radio waves were not strongly reflected by the train's walls.