Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of truckmaker Navistar (NYSE: NAV) drove off a cliff this morning, falling as far as 15% -- before magically levitating, floating back up, and ending the day at a relatively benign 2.5% decline.

So what: History will only show that Navistar suffered this final, minor blip on its stock price. But clearly, something more significant was afoot. What? Well, yesterday the Obama Administration announced new fuel-efficiency standards for commercial trucks, the kind of trucks that -- you guessed it -- Navistar builds.

Now what: Big picture, the new standards call for long-haul trucks to in 2014 begin improving efficiency -- culminating in 23% improvement by 2018. Although this change has been a long time in coming, it seems to have caught investors by surprise and sparked a sell-off on fears that government is once again mucking around inside businesses, imposing rules without regard to cost or what that cost might do to profitability.

I think that's the wrong way to look at it -- and so does Navistar. Rather than fighting the new regs, the company put out a press release yesterday praising the new standards for their uniformity. Whatever you think of regulation in general, Navistar seems to understand that a new set of standards, requiring the building of a new type of truck, is going to boost demand for its product as older, less efficient trucks get phased out in favor of the new breed. That's hardly bad news for its business. In fact, it just might be good news.

Curious to see how this transition plays out? Add Navistar to your Fool Watchlist.