The nation's heightened terror alert didn't seem to slow traffic across the U.S.-Mexico border two days before Christmas as travelers and shoppers crossed into the United States.

In Reynosa, across the Rio Grande from Hidalgo, Texas, traffic on Tuesday flowed smoothly with only a 15-minute wait for cars to cross over.

It was a much different scene Monday, though, the day after the nation's terror level alert was raised from "elevated" to "high."

"Yesterday, it was all day," Reynosa shopkeeper Nancy Gaona said Tuesday. "By car, by foot. It's rare but there isn't a line today."

Then, lines ran across the bridge and past Gaona's store, also extending several blocks into nearby Matamoros' downtown, across the river from Brownsville, Texas.

On Tuesday, it was also better at the border in Tijuana, across from San Diego. Jose Corona, a 48-year-old Tijuana resident who crosses nearly every day to San Diego, said he waited only five to 10 minutes in the express lanes Tuesday, shorter than usual.

"Right now, I'd say the orange alert is no problem," Corona said.

Roger Maier, spokesman for U.S. Customs and Border Protection (search) in El Paso, said the shorter waits could be attributed to people not crossing after hearing about the earlier delays. Also, border-crossers could be heeding advice from the agency like being prepared when they reach the check points and cleaning out trucks to expedite searches.

The upgrade from "yellow" to "orange" on the terror risk scale was based in part on intelligence that Al Qaeda may soon try to pull off a coordinated attack in multiple places to cause mass casualties.

At the San Diego border crossing, inspectors made full use of X-ray and gamma-ray machines to check cargo for smuggled weapons, illegal immigrants and drugs.

Uniformed officers were taken off desk duties and assigned to checking some of the 55,000 vehicles that pass from Tijuana, Mexico, to San Diego every day.

"Everything's focused on the terrorist threat," said Vince Bond, spokesman for the Bureau of Customs and Border Protection.

At Blaine, Wash., the busiest U.S-Canada border crossing west of Detroit, customs inspectors have been checking the trunks and under the hoods of more vehicles since the heightened terror alert, said Mike Milne, spokesman for U.S. Customs and Border Patrol's Northwest region.

Also, he said, "we're running more name checks of occupants in a car, not just the driver."

Still, even with a brisk flow of holiday shoppers and skiers heading to the mountains, heightened security has not caused traffic to back up much longer than usual, Milne said, noting that the longest wait in recent days has been an hour and 15 minutes.

Maier suggested people check the agency's Web site for information on possible delays.