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)
Visible crew/equipment: In several shots of Tuneman in the Jaguar, you can see camera lights reflected in his sunglasses.
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.
Visible crew/equipment: The camera operator and camera are visible reflected in Tuneman's sunglasses. It's especially evident right before he crashes into the water barrels.
Visible crew/equipment: After Keanu steals Tuneman's car there is an overhead shot from a helicopter as he's trying to catch up. The shadow cast by the helicopter is visible at the beginning of this shot.
Visible crew/equipment: When the guard walks past the pillars at the start, on the first pillar you can see a shadow made by the film crew. (00:03:00)
Visible crew/equipment: After the bus exits the freeway, as it drives on the city's streets the forward looking street-level action camera is visible, mounted behind the tire. (00:49:05)
Visible crew/equipment: In the scene after the bus gets off the on ramp and hits a bunch of cars, there is a rear facing shot. The shadow of the camera that is attached to the bus is visible during most of the shot.
Visible crew/equipment: When Payne is going crazy on the subway train, and starts shooting his gun at Jack on the roof, in one shot before Jack drops his gun, you can see a camera come in the shot. (01:42:50)
Visible crew/equipment: As Jack inspects the bus's speedometer for signs of tampering, a camera can be seen in a reflection on the window to Annie's left. (00:44:35)
Visible crew/equipment: As Harry walks out of the office after telling his colleagues to search for their mystery bomber via pension fund files, a boom mic pole is reflected in the left window when he says, "I've seen this a**hole." (00:55:25)
Visible crew/equipment: When Jack is trying to pry open the subway train's doors, a boom mic can be seen mounted on the car's interior, suspended from the ceiling. (01:40:30)
Visible crew/equipment: During the passenger transfers at LAX, a cameraman is visible through the bus doorway two shots before Annie glances over her right shoulder twice. (01:27:35)
Visible crew/equipment: When Jack is running alongside the subway train trying to find a way in, a camera and its operator can be seen on the window's interior reflection. (01:40:20)
Visible crew/equipment: When Jack's Bronco weaves across two lanes of traffic on the highway seconds before throwing it in park to catch up with the bus on foot, a camera can be seen, mounted in the Bronco's back seat. (00:34:15)
Visible crew/equipment: A film truck is reflected in the bus's bumper when Jack exits and steps onto the Suburban. (01:11:15)
Visible crew/equipment: When Jack flashes his badge at Tuneman, a camera's shadow is visible on the pavement. (00:35:00)
Visible crew/equipment: Right after the bus passes 50 mph and arms the bomb, filming equipment can be seen in the Jaguar's vent window reflection. (00:36:45)
Visible crew/equipment: When the credits are rolling, a crew member in a gray shirt on the lower left portion of the screen can be seen waving extras into the street. (01:51:05)
Visible crew/equipment: When the bus is traveling on the shoulder, a camera truck is visible to the extreme left immediately before Annie asks whether or not she should stay on the highway. (00:46:35)
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.