The real problem with the ending, as someone said upthread, is that it ends too abruptly and with the army showing up RIGHT THEN. Here's the gag folks - the goddamn LINE OF TANKS was trundling along /right behind their truck/? That's not horror, that's comedy and cruel, sadistic irony.
The car had been sitting there for hours. The trucks weren't right behind them. Why is it any less "cheap" if he wandered through the mist to find the trucks in a clearing? Rescue was closer than he thought in either scenario. Rescue existed in both scenarios; the tragedy was that they didn't know and they gave up in both scenarios.