UPDATE 1-US highway travel in March down for 16th mth: Govt

(Adds regions with biggest increase and decrease in highway travel)

WASHINGTON, May 20 (Reuters) - Americans drove fewer miles in March for the 16th month in a row, the U.S. Transportation Department said on Wednesday, as the weak economy reduced highway travel.

U.S. highway travel was down 1.2 percent in March from a year earlier, falling 3.1 billion miles (5 billion kilometres) to 245.1 billion miles (394.4 billion km) for the month.

March was the 16th straight month of declining highway travel that began in December 2007, the department said.

For the first three months of 2009, driving was down 1.7 percent, or 11.6 billion fewer miles, from the same period last year.

The South Atlantic region, an area of eight states from Maryland to Florida, had the biggest drop in highway travel in March, down 3.4 percent from a year ago.

The Northeast, made up of nine states from Pennsylvania to Maine, had the biggest increase in miles driven during the month, up 0.5 percent.

The Transportation Department tracks motorists through more than 4,000 automatic traffic recorders operated by state highway agencies. (Reporting by Tom Doggett; Editing by Marguerita Choy)