
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.
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.