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: Aside from the mysterious other trooper(s) reflected in the tarpaulin on the roof near the start, as Keanu Reeves runs past it, you can see the clear silhouette and red light of a cameraman filming the scene. (00:11:30)
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)
Visible crew/equipment: When Jack is talking to Howard Payne from the payphone, you can see the boom microphone's reflection on the phone receiver in several shots. (00:30:00)
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: 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)
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: After Tuneman's Jaguar hits the water barrels, a film crew's truck can be seen out the bus's rear window just before the shot cuts away. (00:40:05)
Visible crew/equipment: When Sam is shot in the shoulder it shows a camera shot from the side of the bus going into a wall. In this camera shot you can see the shadow of the camera. (00:40:15)
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: The side camera is visible in a couple of shots when the bus has to make the tight right turn, after the bus returns all the wheels to the ground, as it smashes into the cop car. (00:45:20)
Visible crew/equipment: A film truck with its crew and equipment is briefly visible in the reflection of a red van four shots after Jack directs Annie onto the shoulder (use pause to get a better look). (00:46:15)
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)
Visible crew/equipment: In the scene where the bus is exiting the highway on that sharp curve there's a medium shot showing the bus from the driver side. Look closely at the driver, it's either a really ugly woman or that's a man in a wig driving the bus. (00:47:04)
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: 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: When the speeding bus takes the really sharp right curve, while it leans over on its left wheels, you can see the crew's tire rig lift under the bus that they used to keep it steady for this stunt. (00:50:10)
Visible crew/equipment: Just after the bus has got on to the empty freeway, there is a long shot of the bus driving off. In this shot, the camera's shadow can be seen to the extreme right of the shot. The shadow is faint, but it is there. (00:51:30)
Visible crew/equipment: After Lieutenant McMahon requests to be flown to the 105 freeway interchange, a camera operator can be seen standing beside an overpass column when the bus and police escort drive by. (00:52:50)
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.