Originally, the scene called for Bond to jump a motorcycle onto the roof of a moving train, which was packed with folks riding the rails illegally. India is working hard to stop this practice, and the local government asked the production team to remove the roof riders from the film (don't tell the boys from Slumdog Millionaire...).
The crew has obliged, and passengers will sit safely inside the train while Bond roars over their heads on his bike. Either way, we know for sure that Bond will wind up killing a lot of bad folks and bedding a lot of hot women. We call that a win-win-win situation.