Continuity mistake: Near the end of the film when Keanu Reeves and Dennis Hopper are wrestling on top of the subway, if you watch Keanu's left wrist you notice he is wearing a watch. Yet throughout the scene it is obvious that the stunt double has no watch, because in the extreme action scenes, there are no signs of it anywhere on his wrist.
Continuity mistake: On the subway train where Payne opens the money bag, a dye pack goes off and leaves a purple stain on the dead man's handle. But moments later in the shot where Payne stops firing his machine gun at the ceiling, the stain has vanished. (01:42:35)
Revealing mistake: Before Jack rips the door off the Jaguar, he speeds ahead of the bus and then opens the driver's door at highway speed. At 50 MPH there would be a lot of air resistance, yet Jack opens the door effortlessly.
Other mistake: As Traven is about to slide under the bus on the small trolley, you can see his feet are only just going to get under the bus. Cut to a camera shot from the side, and now the front of the bus is significantly higher.
Continuity mistake: The 2 SWAT team members are not visible on the preceding truck between two shots. (01:12:55 - 01:13:32)
Continuity mistake: Right after the bus jumps the gap, Jack hugs Ortiz. Immediately following you can see the reflection of the stairwell at the front in the mirror. The stairwell and door are both fine, after having been blown off when Helen died. (01:07:00)
Visible crew/equipment: As the end credits are starting, tracks used for a camera dolly can be seen along the left side next to the buildings. (01:50:55)
Continuity mistake: When Jack starts wiggling the train's pole, his hands switch places between shots. (01:46:05)
Visible crew/equipment: A camera crane is visible in the bus's rear window reflection just as it enters the empty 105 freeway via police escort. (00:53:35)
Visible crew/equipment: When McMahon is giving Jack directions to the vacant 105 freeway, a well-dressed crew member wearing sunglasses and a big grin is visible sitting in the aisle of the bus. (00:49:50)
Continuity mistake: As Annie shouts at Sam and suggests he drive over the line of cars up ahead, the bus passes by a couple of bridges - visible through the side window where she and Helen are seated. But no bridges were visible anywhere at all when Sam first noticed the endless line of gridlocked traffic just seconds before. (00:33:55)
Audio problem: When Sam is being loaded onto the trailer, Jack's mouth is visibly closed when we hear him say, "You got him? You got him?" (00:58:30)
Continuity mistake: At the very start of the movie, in the basement, you see a security officer walk past some numbered steel pillars, he walks past the pillars numbered "15" twice. Fixed in the Blu-Ray. (00:03:35)
Revealing mistake: In the scene in the subway Denis Hopper has again used an explosive jacket like that used at the start of the film, which is detonated if the remote trigger is released. However when on the subway train, Denis takes the remote back from Sandra Bullock and it is seen that the trigger is quite obviously released and Denis pushes it back in.
Continuity mistake: After the bus has left the freeway and enters the city for the first time, there is a scene where Annie is driving the wrong way down a street and Jack can be seen standing right next to her. She pulls the bus onto the right side of the road and Jack puts the cell phone to his ear. In the next shot, he repeats the same action.
Visible crew/equipment: When Jack is talking to Howard from the pay-phone, you can see the boom microphone's reflection in the phone in several shots.
Revealing mistake: When Jack is fighting Dennis Hopper on the roof of the subway train, a piece of paper falls off one of them and then stays surprisingly still considering they're on a speeding subway train.
Revealing mistake: When Harry and Jack arrive at the building at the start in the police car, you can see the tire skidmarks on the road from previous takes. (00:05:05)
Revealing mistake: After Jack has taken command of "Tuneman"s car, in the wide shots of them chasing the bus you can tell it's not Keanu Reeves driving. The stunt driver has slightly longer hair in a more squared crew cut.
Continuity mistake: In the scene where Jack is fighting Dennis Hopper on the roof of the subway train we see Jack lying on the top of the train getting punched by Dennis. We briefly cut away, and then back to Jack and the corrugations on the train roof have rotated through ninety degrees.
Answer: If they had, there might have been the possibility that to get to these routes they would have to go down a different road and depending on which route they take they might have to slow down to make the turn which would likely cause the bus to drop below 50 mph. Better to just keep going straight and keep the bus going. There's also the possibility that had they taken a different route, they would have to deal with a lot of traffic especially if there was traffic stopped at a red light. By using the highway, there'd be no traffic lights and less traffic to deal with.