It quickly became apparent Friday that the driver of a black GMC pickup speeding along Interstate 26 had no idea an unmarked S.C. Highway Patrol cruiser was behind him.

The truck was already traveling about 10 mph over the posted 70 mph speed limit when it abruptly shifted to the left lane, then back to the right without signaling.

Highway Patrol Lance Cpl. J.L. Davis followed the pickup in his unmarked Chevrolet Impala for a little while to see what other chances the driver would take. He watched the pickup slow to 70 mph and then speed up to 82 mph as it passed a marked patrol cruiser stopped on the shoulder.

Davis hit the blue lights, and the pickup pulled over to the shoulder -- right in front of a third patrol cruiser that had pulled over yet another motorist.

Welcome to the Highway Patrol's new aggressive enforcement on a deadly 22-mile stretch between Jedburg and Interstate 95.

The crackdown, which began Monday, comes in the wake of a Post and Courier Watchdog analysis this year that identified "death zones" around Ridgeville and Harleyville that had fatality rates three times higher than other stretches of I-26.

Davis is one of four troopers driving unmarked patrol cars along that stretch at any given time, particularly on weekends when the wrecks seem to happen most often.

Leading up to the crackdown, there was some talk about how troopers would have little tolerance for speeding, but the patrol said it is leaving it up to the troopers' discretion.

Davis chooses to be on the forgiving side. He gave the GMC pickup driver a ticket for going 79 mph instead of the 82 mph at which he was clocked. He also gave him a written warning for the improper lane changes.

"I'm trying to make people be aware, but I'm also trying to use a firm hand while doing it," Davis said upon returning to the patrol car.

There was definitely a lack of awareness in the death zone Friday. Over and over, cars sped right by the unmarked Impala, oblivious to the lights in the back window and the radar on the front window.

"I just really believe people get so distracted that they're not paying attention," Davis said. "If you're paying attention, you would be able to realize I am in a law enforcement vehicle."

Almost on cue, a black Chevrolet Cobalt passes the Impala at 83 mph and then -- as if suddenly noticing the uniformed trooper in the driver's seat -- slowed down.

"Too late, buddy," Davis said, hitting the blue lights.

The Highway Patrol released data showing that 25 people died between 2007 and the end of 2009 between mile markers 194 in Jedburg and 172 near Harleyville. All 25 involved wrecks in which a single car ran off the road, often because a driver was speeding, over-corrected, wasn't paying attention or fell asleep.

Davis doesn't always pull someone over immediately. He likes to see what kind of risks the person is willing to take and what it will take to slow him down or get him to pay attention.

He pointed out that drivers seem to obey the law more when they're traveling the wide-open stretches of the highway between Charleston and Summerville. But something happens when they get to the two-lane stretch past Summerville toward Columbia; people take more chances.

He once caught someone speeding in the low 100s on this stretch.

Perhaps it's because the speed limit increases to 70 mph, or perhaps it's because most of that stretch is surrounded by trees, leading to the sense that no one is watching. Davis doesn't know the answer, but either way, he finds the risk-taking scary.

"It's kind of frightening to see it, especially as a Highway Patrol trooper," he said. "It scares me."

Heading back east toward Charleston, Davis saw another thing that scared him: two women in separate vehicles speeding about 81 mph with less than a car length between them. Davis hit the blue lights behind the second car, waved the driver over to the shoulder and then pulled over the front car.

The drivers of both cars told Davis separately that the other had been driving recklessly. One woman told him that the cat-and-mouse game had been going on for about an hour.

"I'm glad I stopped them because it looked like it was about to become a bit of road rage," he said.

He gave each woman a warning for speeding. While doing so, a string of four or five cars following closely together scream by until one hit the brakes, causing a cloud of smoke and a mysterious thump.

Just another reason drivers should give themselves more distance, Davis said. "You will be amazed how often that happens," he said.

Davis is curious to see how drivers respond to the new enforcement, especially with the first full weekend coming up.

After all, Friday morning was a relatively slow time for traffic.

Reach Andy Paras at aparas@postandcourier.com, 937-5589 or on twitter at twitter.com/andyparas.