Questions and Answers About EMF Electric and Magnetic Fields Associated with the Use of Electrical Power.
January 1995.

Your EMF Environment

Q. What typical EMF sources do I encounter when traveling?

A. Inside a car or bus, the main sources of 60-Hz magnetic field exposure are those you pass by (or under) as you drive, such as power lines. Car batteries involve DC rather than AC. Alternators can create EMFs, but not at 60-Hz.

Most trains are diesel-powered. Some electrically powered trains operate on AC, such as the Baltimore- Washington commuter train. Measurements taken on this train in 1991* showed 25-Hz magnetic field strengths as high as 500 mG in the passenger areas at seat height. Other trains, such as the Washington, D.C., Metro and the San Francisco Bay Area Rapid Transit, run on DC, but even these trains are not free of AC fields. Areas of strong AC magnetic fields have been measured on the Washington Metro close to the floor, presumably near equipment located underneath some subway cars. Train motors and other equipment can create alternating fields at higher than 60 HZ frequencies. In addition to sources of magnetic field exposure from the train itself, train passengers are exposed to magnetic fields from sources the train passes on its route