Houston ? Hurricane Rita closed in on the Texas Gulf Coast and the heart of the U.S. oil-refining industry with howling 140 mph winds Thursday, but a sharper-than-expected turn to the right set it on a course that could spare Houston and nearby Galveston a direct hit.

The storm’s march toward land sent hundreds of thousands of people fleeing the nation’s fourth-largest city in a frustratingly slow, bumper-to-bumper exodus.

“This is the worst planning I’ve ever seen,” said Judie Anderson, who covered just 45 miles in 12 hours after setting out from her home in the Houston suburb of LaPorte. “They say we’ve learned a lot from Hurricane Katrina. Well, you couldn’t prove it by me.”

In all, nearly 2 million people along the Texas and Louisiana coasts were urged to get out of the way of Rita, a 400-mile-wide storm that weakened Thursday from a top-of-the-scale Category 5 hurricane to a Category 4 as it swirled across the Gulf of Mexico.

The storm’s course change could send it away from Houston and Galveston and instead draw the hurricane toward Port Arthur, Texas, or Lake Charles, La., at least 60 miles up the coast, by late today or early Saturday.

But it was still an extremely dangerous storm – and one aimed at a section of coastline with the nation’s biggest concentration of oil refineries. Environmentalists warned of the possibility of a toxic spill from the 87 chemical plants and petroleum installations that represent more than one-fourth of U.S. refining capacity.

Gulf coast residents try to evacuate Houston on Interstate 45 on Thursday in preparation for Hurricane Rita. During the bumper-to-bumper exodus, many vehicles ran out of gas, and officers along the highway carried gas to motorists.

Forecasters warned of the possibility of a storm surge of 15 to 20 feet, battering waves, and rain of up to 15 inches along the Texas and western Louisiana coast.

The evacuation was a traffic nightmare, with red brakelights streaming out of Houston and its low-lying suburbs as far as the eye could see. Highways leading inland out of Houston, a metropolitan area of 4 million people about an hour’s drive from the shore, were clogged for up to 100 miles north of the city.

State officials hoped to transport more than 200,000 gallons of gas to service stations that reported running out of fuel. Police officers and National Guard trucks carried gas to motorists whose tanks were on empty.

By late Thursday, the traffic bottlenecks were improving, with congestion easing on many major arteries leaving Houston, said Robert Black, spokesman for Gov. Rick Perry.

Rather than sit in traffic, some people walked their dogs, got out to stretch or switch drivers, or lounged in the beds of pickup trucks. Fathers and sons played catch on freeway medians. Some walked from car to car, chatting with others.

With temperatures in the 90s, many cars were overheating, as were some tempers.

To speed the evacuation, the governor halted all southbound traffic into Houston along Interstate 45 and took the unprecedented step of opening all eight lanes to northbound traffic out of the city for 125 miles. I-45 is the primary evacuation route north from Houston and Galveston.

Along the coast, petrochemical plants began shutting down and hundreds of workers were evacuated from offshore oil rigs. Environmentalists warned of a worst-case scenario in which a storm surge pushed spilled oil or chemicals from the bayous into the city of Houston itself, inundating mostly poor, Hispanic neighborhoods on its south side.

Gov. Perry said state officials had been in contact with plants that are “taking appropriate procedures to safeguard their facilities.”

In New Orleans, Rita’s steady rains Thursday were the first measurable precipitation since Katrina. The forecast was for 3 to 5 inches in the coming days – dangerously close to the amount engineers said could send floodwaters pouring back into neighborhoods that have been dry for less than a week.

Katrina’s death toll in Louisiana rose to 832 on Thursday, pushing the body count to at least 1,069 across the Gulf Coast. But workers under contract to the state to collect the bodies were taken off the streets of New Orleans because of the approaching storm.