Visible crew/equipment: In the scene where Jack is taking off the handcuffs of the guy who shot Sam, you can see the top of a bald crew member's head with headphones on behind them.
Visible crew/equipment: On the train, Jack hears Mac saying the track isn't finished, then Jack becomes aware of the broken emergency stop button. When Jack walks back over to Annie and tells her they have to jump, we can see the reflection of the standing camera operator on the right door's window, and the reflection of a crouching crew member (possibly boom operator) on the left door's window. Definitely crew given they're meant to be alone on the train. (01:45:55)
Continuity mistake: In the last 20 minutes of the movie when Howard Payne is on the train and offers Jack some money, Howard opens the money bag and gets sprayed with purple paint. When Howard climbs on top of the train to fight Jack, all of the paint is gone.
Continuity mistake: At the beginning, when the employees are getting into the elevator, there is a close view of the man at the front pushing the button with his finger, but when it cuts to a wider shot, he is taking his thumb away from the button, instead of his finger. (00:04:35)
Visible crew/equipment: When Jack is running beside the bus and breaks the window to get the driver's attention, there's a reflection in the window of the bus of a cameraman (wearing a baseball cap) running alongside the camera. In the next scene where the bus pulls ahead, the reflection of the camera is larger and more noticeable. (00:34:35)
Continuity mistake: After Jack shoots Harry in the leg, Denis Hopper runs out the door which is wide open. The explosion shot (seconds later) happens and we see the door completely shut. (00:22:05)
Visible crew/equipment: Close to the beginning of the film we see Jack in a coffee shop and his friend walks in. When they both leave and Jack goes to his car, a cameraman is reflected in the car window after the palm tree. (00:26:40)
Continuity mistake: At the beginning of the movie after Jack has hooked up the crane from outside to the lift, there is a shot of the crane outside, and the line going through the vent. If you look closely there is a pipe in front of the vent, yet when the crane goes through the vent, the pipe has vanished. (00:14:20)
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: When Jack handcuffs Ray to the metal handrail, Ray's right wrist has the double strand bars facing up and single strand bar facing down, but when Jack tells the passengers about the gap and then uncuffs Ray before the jump, the handcuff's single strand bar is facing up on his right wrist.
Revealing mistake: The Jaguar owner holds up the piece of paper with "bomb on bus" written on it, then he loses his grip on it, and when the paper lands directly on the bus windshield, the stunt wires are visible at its sides. (00:37:35)
Continuity mistake: The 2 SWAT team members are not visible on the preceding truck between two shots. (01:12:55 - 01:13:32)
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)
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)
Continuity mistake: When Jack starts wiggling the train's pole, his hands switch places between shots. (01:46:05)
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)
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: When the crane breaks free from its bolts and starts flying towards some ventilation windows, it obliterates the upper pair. However in the next view from within an air duct, both of these windows just swing open freely as the crane busts through, and yet they barely appear to have suffered a scratch or bend in the process. (00:15:00)
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 the crane is torn out of the floor and flies towards the ventilation window, from a shot behind, the holes on the base (where the screws used to be) are gone. (00:14:30)
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.