This Sylvester Stallone nail-biter uses one of those reality-based premises to jack up its suspense quotient: What if you were midway through a highway tunnel under a body of water and something happened to seal it up at both ends, and many things inside the tunnel were on fire, and also the river was getting heavy? Well, OK, it’s a little vague on paper, but in Daylight it’s downright preposterous. No matter how effectively director Rob Cohen keeps the audience’s adrenaline flowing, it’s way too easy to remind yourself that this could never happen, at least not the way they’ve constructed it here.

First of all, a caravan of trucks carrying highly flammable toxic waste (a pretty, bright yellow powder—jonquiladine?) would have to be dispatched to dump the stuff (sal of daffodiliac?) illegally somewhere on the other side of the river. Then, three gleeful, wahooing, really crazy white punk-rock hooligans with Mohawks and leather jackets would have to carjack an Asian diamond dealer’s luxury sedan and drive it into said tunnel to escape the policeman who happens to be right behind them thanks to the car’s sophisticated security system.

These punks would have to be too crazy to drive at a normal pace, so they’d careen around, causing havoc and eventually crashing into one of the trucks carrying an illegal load of buttercupanide. Instantly, almost everyone in the tunnel would be torched except for a handpicked dozen racially, economically, and sexually varied survivors. And entering the mouth of the tunnel just at that moment would be Kit Latura, ex-head of the Emergency Medical Service, reduced to driving a cab for the exorbitant tips of high-strung yuppies. Latura, sensitive maverick, beefy but renegade man of action, is the only person with enough tunnel know-how and sheer guts to get these good people out safely.

Should all these circumstances unite to result in just this situation, however, you may find yourself among the survivors’ number—with the four young convicts (one of whom is Stallone’s son, Sage—a babe), the elderly aristocrats, and their too-doted-upon dog, the whining couple with their whining child, the cocky head of an athletic-gear firm, the good-hearted tunnel guard who’s just fallen in love, and the girl playwright heading back out of the big city. These people’s backstories are actually fairly interesting; I wouldn’t have minded spending more time in Madelyne Thompson’s rat-and-roach-infested apartment while she sparred with her muse and unforgiving theater producers, even if she is played by Amy Brenneman. And Viggo Mortensen sparkles as usual in a too-short performance as Roy Nord, all cheekbones and self-confidence, each shoulder looped with pricey adventure gear meticulously calibrated to keep the risk-as-leisure-activity entrepreneur alive.

The big lug behind the taxi’s wheel, of course, knows better. Unfortunately, Stallone is the last person you’d want giving life-or-death orders; you’d better hope there’s someone, anyone else who knows tunnel construction and rescue techniques, because you can’t understand a word this guy says, unless yonder lies the castle of his father. But the characters don’t seem to have a problem with Stallone’s highly approximate form of English. His announcement that “Shumma hazta chicken duh Mahatta in” doesn’t provoke the realistic response (a chorus of “Wha?,” “Huh?,” and “Speak up, for God’s sake!”) but actually prompts the survivors to volunteer for the task of checking the Manhattan end of the tunnel. In fact, the setting is so murky and wet and anti-acoustic that no one sounds clear; Vanessa Bell Calloway’s character, Grace, speaking from aboveground, has a lilting Caribbean accent that is the only fresh air in this movie.

Stallone does his best to seem heroic and self-effacing; he should just keep his mouth shut and pick heavy things up with his short, pillowy arms. The script (by Leslie Bohem) finds something disastrous to threaten our brave adventurers every time the action lags—they perch on overturned cars, fight off hypothermia in an underground chapel, bicker tensely while waiting for Latura to return from some solo jaunt, and every time, another giant boulder of action comes rolling their way to get them moving again. And as tense as it gets, there’s never a satisfactory explanation of how the tunnel became “sealed at both ends.” Throughout, the question nags: Why can’t they just walk out?

In spite of the sketchy exposition, the action’s stop-start motion, and the fact that some of the characters are so annoying you’d rather see them flattened by a fireball than spiritually redeemed, Daylight clips along nicely. Cohen makes sure to keep the audience apprised of where we are at all times—the tunnel’s structure makes sense, and adds to the feeling of claustrophobia that is this movie’s raison d’etre. Stallone has a very tense sequence entering the tunnel through a gigantic, Modern Times-ish exhaust system, and aboveground, engineers and city planners discuss the tunnel’s construction and history.

By the way, it seems to be the Holland Tunnel, although the script doesn’t specify, perhaps worried that the Lincoln Tunnel would sue. Construction geeks will love the nuggets of inside dope offered up by Bohem’s script; for all the macho fantasy playacting going on below, aboveground the situation is all about civic neglect, know-nothing local agencies, and the disastrous results of cost-cutting. At one point a model for the project is dusted off—it was the height of engineering sophistication at the time and, as one character says, was built when “we were looking back at World War I.” Every so often, in between the squeal of rats and mush-mouthed posturing, Daylight offers little glimpses of that history.