While GM claims the Chevy Volt "has always been safe to drive," the auto manufacturer is making some slight physical enhancements to the plug-in hybrid this month, to ensure drivers that their vehicle won't spontaneously catch fire weeks after a major accident. That wasn't necessarily a major worry, mind you, as the reported fires have only occurred in the lab, specifically in side-impact crashes where the battery was punctured and the "owner" failed to disconnect the battery afterwards.

That won't stop GM from adding a battery coolant temperature sensor, a tamper-resistant bracket for the battery coolant tank, and a large metal shielding bracket for the underside of the car, though, and the National Highway Traffic Safety Administration (NHTSA) seems pleased with the fix, having crashed a new Volt with the brackets and sensors installed on December 22nd. The government organization says it hasn't completely finished investigating the Volt fires and will continue to monitor the crashed car, but for now things are looking up. Wired reports that a voluntary recall of all Volts will begin in February, and new cars will come with the changes starting this month.

Speaking of new cars, the Volt reportedly had its best month of sales ever this December despite the ongoing investigation, moving 1,519 cars, bringing the lifetime total sales to 7,997. That's still a good bit shy of GM's 10,000 sales target for 2011, but it's not bad: the recent Chevy Corvette, for instance, sold only 1,038 vehicles in December, for a total of 13,164 this year.