By Michael Barnett,Knight Ridder Newspapers

WASHINGTON – Acadia National Park. The Outer Banks. Myrtle Beach. The Hamptons.

These summer tourist hot spots promise fun, relaxation and something much less appealing: a lot of traffic congestion getting there.

They’re three of 25 scenic travel destinations with the worst summer traffic tie-ups, according to a report released Thursday by three vehicular-transportation advocacy groups.

“Many of us will spend the beginning and end of our trips in traffic comparable to or heavier than our everyday commutes,” Greg Cohen, president and chief executive officer of the American Highway Users Alliance, said at a news conference Thursday. He was joined by representatives of the automobile club AAA and TRIP, a nonprofit transportation organization. The groups are using the report to urge Congress to pass a long-overdue transportation bill.

The Oregon Coast near the Willamette Valley; Virginia’s Tidewater region; the Maryland/Delaware shore; the lakes and camping sites near Branson, Mo.; and North Carolina’s Outer Banks are the five destinations with the worst traffic bottlenecks, according to the report. Sixteen of the 25 places are in East Coast states. The roads leading to California’s Napa Valley and Lake Tahoe on the California-Nevada border also made the list.

Cambridge Systematics, the Massachusetts transportation-research firm that conducted the study, asked states’ transportation departments to identify traffic bottlenecks near popular scenic tourist destinations. It ranked the sites based on their number of traffic delays, the total number of summer trips and the estimated delay per trip.

The report was an effort to draw attention to the stagnating transportation bill, which provides billions of dollars in highway money to states that could be used for congestion-reduction projects. On Thursday, lawmakers announced they needed more time to pass the bill and expected to extend its deadline to ensure that federal and state agencies continue to receive transportation money. The deadline has been extended seven times since the last bill expired in September 2003.

This summer is projected to be the busiest ever on the roads, with 328 million recreation trips of more than 50 miles each expected, according to the study, an increase of 2.3 percent from last summer.

For motorists planning to visit those congested areas, the report suggests avoiding peak travel times, such as Friday and Sunday afternoons, finding alternatives to driving and allocating ample time for trips.