Continuity mistake: When the security guard is trapped underneath the truck, in daylight the amount of water he is drowning in changes. From the front angle he is also most covered in water and from the side angle he has more time.
Factual error: In the beginning of the movie, the explosion in the Holland Tunnel is caused when a car crashes into the trucks carrying toxic waste barrels. In real life, it is against the law for vehicles carrying hazardous chemicals to use any of the tunnels. Even if the drivers didn't know this, which is highly unlikely, they would have been pulled over by the Port Authority cops as soon as they headed for the entrance - lots of yellow barrels would be a bit suspicious.
Plot hole: The main accident is a crash involving toxic waste, which seals the tunnel, yet no one has any trouble breathing, or even has so much as irritated eyes.
Factual error: Even if the survivors were in their vehicles, a raging inferno like that would seriously damage their skin. Even if a vehicle can protect you from being set on fire, I think the chances of being skin burned and blistered are especially high. First of all, the prison bus had those open diamond holes on the side of the bus. Also, I believe someone's car window was open, so they should have been set on fire.
Continuity mistake: When the tunnel caves in as a result of the explosion, the cars about to enter it come to a stop in almost a straight line. When Stallone gets out of his limo, the cars are now scattered everywhere. Then, when he goes back later to the collapsed entrance, the cars are not only in different positions, but some have changed in make and model as well.
Other mistake: When the thieves are "escaping" in the tunnel, there is enough space for them to drive fast and cut in and out between other vehicles. This would be impossible because traffic was jammed in and out of the tunnel.
