Americans drive 1.4 billion fewer highway miles. (CNN)

Americans drove 1.4 billion fewer highway miles in April than they did in April 2007, the Department of Transportation said Wednesday.

Americans have driven 20 billion fewer miles overall this year, the Transportation Department says.

That marks the sixth consecutive monthly drop and coincides with record gas prices and an increase in transit ridership, Transportation Secretary Mary Peters said.

April’s drop is more than three times larger than the drop from March 2007 to March of this year, which was 400 million fewer highway miles.