Researchers say a new study of mobile phone records shows people rarely stray from familiar areas.  Researchers say the findings could be useful to urban planners addressing problems as varied as traffic forecasting and emergency preparedness.  VOA's Jessica Berman reports from Washington.

The study tracked the mobile phone use and movements of 100,000 people over a six-month period. 

The participants were selected from a pool of six million mobile phone users in an undisclosed country. 

Each time a call was made or received, or a text message recorded, investigators noted the location of the relay tower servicing the mobile phone.  They also recorded calls to two locations most frequently used by the mobile phone user.

Researchers found the calls were usually made to and from home and work within a five-kilometer radius or area around the tower. 

Using the same model, they could also tell what percentage of calls were made from a distant location.

Marta Gonzalez of Northeastern University in Boston, Massachusetts is the study's lead author.  Gonzalez says predictably, mobile phone users by and large stayed close to home.

"We really found that in fact 70 percent of the time, most of the people were found in two preferred locations," she said.

Gonzalez says less than one percent of cell phone users regularly ventured 500 kilometers from home.

Gonzalez says mobile phone records provide an easy and readily available means of measuring the movement of populations, which she says could be useful to urban planners in a number of ways.

"When you have epidemics in a given place, you want to know which are going to be the most connected place according to the transport of people from one place to the other so you can take measures in advance," she added.

With the number of mobile phones worldwide estimated to be three billion and growing, mobile phones have proved indispensable in coordinating rescue and relief efforts during natural disasters such as the recent Chinese earthquake.

The study on mobile phone usage is published in this week's issue of the journal Nature.