Do cash incentives alter driving habits?

From the Seattle Times:

Do cash incentives alter driving habits?

The 400 volunteers in the Puget Sound Regional Council's "Traffic Choices" study have been paying virtual tolls since July. Devices mounted on their dashboards track where they travel and transmit the information to a central computer. Charges are deducted from prepaid "endowment accounts."

Those accounts are just play money. But if there's anything left in them when the experiment ends in February, participants get to keep it — in real dollars.