Continuity mistake: When Jack is on the bus and is coming up to the construction site, if you look out of the bus to the left the scenery changes, from having grass on the left before the construction site, to having dirt between shots. (00:49:30)
Continuity mistake: When the bus jumps over the gap in the freeway, when they take off, Jack shields Annie with his own body, but when it shows an exterior shot of the bus when they have landed, Jack is gone, then he comes back again in a different shot.
Continuity mistake: After the first bus blows up, Jack hears the phone ringing. It is a two phone stand. When Jack first reaches for the phone to answer it you can see he answers the phone on the right hand side. To the right of the phone you can only see trees to the right side. In every scene after that, he is on the left hand side phone.
Continuity mistake: When Jack and Annie arrive in the ambulance, as Jack leaves the ambulance he closes the side door. However, when Annie gets bored and gets up to leave the ambulance via the same exit that Jack did earlier, that door is now open.
Continuity mistake: Traven drives at high speed down the hard shoulder of the freeway to get to the bus to avoid the big traffic jam. When Traven cannot get on the bus, the black Jaguar XJS is now close at hand, which would have been impossible - it was way back in the traffic and couldn't have got to him that quickly.
Continuity mistake: When Annie swerves to avoid the schoolteacher and the kids, in the previous shot of the kids and the schoolteacher, they have already stepped out onto the road and are crossing, yet when the camera cuts to a view looking out the bus the schoolteacher and the kids are just stepping off the curb and walking across. (00:48:50)
Continuity mistake: When Howard Payne gets off the elevator with Harry held hostage, Jack walks off the elevator and there is a light on the wall that Jack passes twice and/or turns the small corner twice. (00:21:10)
Continuity mistake: When Jack has caught up to the bus on the freeway then asks the driver to open up, the driver starts driving off, and Jack tries to catch it but fails. When he is standing on the freeway, look behind him, the red car with its passenger window down is driving past him, but in the following shot the red car is there again swerving to avoid him. (00:33:30)
Continuity mistake: In the cafe, Jack shouts to Bob "Have a good one" and holds his arm out with his coffee in his hand. When the shot changes and Jack is turning back to the counter, his coffee has swapped hands. (00:26:20)
Continuity mistake: After Jack discovers the camera, we see what the camera is seeing in Howard's apartment on the screen. Where is Jack? He was just standing next to Annie. He should be front and center in the shot but he is nowhere to be found. The shot is wide enough that even if he was leaning out the door we'd still see him. When we see the monitor again later, he is there.
Continuity mistake: When Jack is under the bus there is a shot from the driver's side that shows the vehicle pacing the bus. The two people that were standing on that vehicle are gone. They are back the next time we see it (when the bolt snaps).
Continuity mistake: When Sam gets shot, Annie takes the wheel back. We see the bus swerving toward the wall as Annie is grabbing the wheel. In the next shot inside the bus, she repeats the action.
Continuity mistake: Payne has just forced his way into the subway car with Annie as his hostage. Jack shoots the lock off an emergency door in pursuit. The bullet holes on the two sides of this door do not match. (01:40:05)
Continuity mistake: In the elevator scene, when Jack is on top of the elevator, Payne sends the elevator to floor 46 from floor 28, but a second later when Jack looks up at the camera, if you look very closely, you can see he is on floor 15...16...17..., but he's supposed to go up from 28 to 46. (00:02:10 - 00:05:15)
Continuity mistake: When the cops arrive at Payne's house, the front passenger door of the silver car closes. However, in the next shot it is open. (01:19:45)
Continuity mistake: When Helen tries to get off the bus, Payne blows up the door. The door is open. However, in the next shot, when looking over Jack's shoulder, the door is closed.
Continuity mistake: As McMahon watches Harry stumble out of the bar, he takes a puff of his cigar. Between frames, his right hand quickly moves from the cigar to the counter-top. (00:26:30)
Continuity mistake: When Norwood and McMahon break out their maps after hearing about the gap, their platform truck passes a large overhead freeway sign on the right, as seen in a rear window reflection. But a second later, when McMahon insists that the freeway is finished, the sign is roughly 100 yards away instead. (01:02:40)
Continuity mistake: At some point before the bus slams into a tow truck and sends a car flying, a large pile of shrubs appears on the curb's edge near the bystanders who start running for cover. (00:46:30)
Continuity mistake: In the cafe, when saying goodbye to Bob, Jack's coffee cup changes hands between shots. (00:27:20)
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.