Each one was given “endowment accounts” of “virtual cash” which was charged every time they used certain highways or were on the road during rush hour. The information was transmitted by monitoring devices on their vehicle’s dashboard. At the end of the experiment (February, 2006), any remaining virtual cash was exchanged for the real thing.
Note that the amount of virtual cash at the beginning of the experiment was different for each volunteer as it was based on driving habits.
The goal of the experiment was to see how financial incentives and disincentives, such as toll roads, would have on people's driving habits. The data gathered so far among the volunteers has fluctuated wildly. Some couldn’t change their driving habits due to their lifestyle (e.g., driving children to school in the morning.) Others, like Bill Tan, reduced his driving to the point that the study manager contacted him to see if the monitoring device had broken.
Results of the study will be available later in 2006.