It seems as though you can barely drive a mile without seeing them: the shredded remnants of truck tires on the highway.
They can be a hazard, especially to motorcyclists. And with high temperatures, tire debris from 18-wheelers called "gators" in the trucking industry are a more common sight on freeways.
Rochelle Jenkins, a spokeswoman for the state Department of Transportation, said gators must be picked up by hand and have been keeping maintenance workers busy.
"We have sweepers, but actually, the blown tires are too large for them," said Jenkins. She said maintenance workers told her gators are a constant problem that can keep them occupied for most of the day.
The origin of gators is in dispute, especially the idea most gators come from capped or retreaded tires. Retreading is a process that saves money by shaving down old tires to their casing and attaching and bonding a new exterior.
"On these extremely hot days, the adhesive that holds these treads together gets hot enough that they lose adhesiveness," said David Decker, director of operators at Western Truck School in West Sacramento.
But Rod Stevenson, a manager at North State Tires in Yuba City, said retreads are economical, can double the life of a tire, and if manufactured properly, are as safe as new tires.
He sells new tires, which can cost up to $600, and retreads, which are less than $200. Problems arise from disreputable retreaders who take advantage of the lack of regulation and make tires that fall apart within weeks, he said.
They "don't take the extra steps that we do," such as X-raying tires for flaws and refusing to retread old tires, he said.
"People oversimplify it. And I completely understand it," said David Stevens, managing director of the Tire Retread and Repair Information Bureau.
He said gators also come from regular tires that blow out.
Michael Shaw, spokesman for the California Truckers Association, said debris happens because truckers travel so many miles and the big rigs have so many tires.
The key is trying to prevent blowouts.
"Proper maintenance of our vehicles is critical to our success," Shaw said, adding that truck drivers are required by law to inspect their vehicles every time they set out.
"It's more than just going up and kicking the tires," said Decker. "They're running their hands over them to look for cuts, abrasions and bulges."
Stevens and Shaw cited a 2008 study from the National Highway Traffic Safety Administration that showed retreaded tires were no more likely to blow out than new tires. The study also indicated that tire defects occur more frequently during summer.
The same study estimated the impact of gators on U.S. highways. It reported that less than half a percent of crashes and fatalities were prompted by drivers swerving to avoid debris, and an average of 55 people were killed per year in truck accidents in which the trucks were found to have tire damage.
Statistics maintained by the California Highway Patrol make it hard to tell how big a problem gators are, but spokesman Adrian Quintero said they don't come close to being the biggest risk for state drivers.
"Ladders are the No. 1 call we get," said Quintero. "Mattresses are a close runner-up after that."
Quintero said any road hazard should be considered an emergency. "Dial 911 immediately and give us that information," he said.