Heavy Rain, Spray, and a Schedule to Keep
An expressway bus is traveling at 75 km/h in a 70 km/h zone during a heavy rainstorm at night. Visibility is about 120 m, and water is pooling in the left lane. The bus is 25 m behind a large truck that is throwing up spray; the wipers are leaving streaks. The driver has 38 passengers, is 20 minutes ahead of timetable, and the next interchange is 6 km ahead. The tire tread is 3.0 mm. The driver feels a brief light steering pull when crossing a puddle. The bus has ABS and stability control, and the driver's foot is on the accelerator to keep time. A following car is 15 m behind the bus. The road curves gently to the right beyond the truck.
1. Identify the main hazards and explain why 75 km/h is unsafe in these conditions.
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The main hazards are standing water and possible hydroplaning, the truck's spray reducing visibility, streaked wipers, the gentle right curve, and the car following only 15 m behind. At 75 km/h the bus is already above the 70 km/h limit, and the 25 m gap to the truck gives less than two seconds' following distance; in rain, that is far too small. The brief steering pull on the puddle is a warning that the tires are losing contact with the road. ABS and stability control help with braking and yaw, but they cannot create grip where water separates the tire from the surface. The 3.0 mm tread is legal but wet performance is reduced compared with a new tire. The driver should reduce speed smoothly and increase the gap, not rely on electronics to compensate for speed and spray.
2. What actions should the driver take in the next 30 seconds, and what should he not do?
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He should ease off the accelerator gently, avoid any sudden braking or steering, and keep both hands on the wheel. He should increase the following distance to at least four seconds, which at 75 km/h means well over 80 m, and drop speed to a level where the puddle does not produce a steering pull. He should use the wipers at a higher setting, keep headlights on, and look further ahead through the curve rather than fixating on the truck's rear. He should not overtake in the spray, use hazard lights as a substitute for slowing down, or stop on the hard shoulder unless there is an emergency. If visibility falls below about 50 m or the steering pull becomes stronger, he should leave at the next interchange rather than press on. The 20-minute early arrival is irrelevant.
3. How should the driver manage the timetable and the tailgating car while maintaining safety?
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The driver should accept a delayed arrival and inform the operations manager that weather and traffic are affecting the run. Passengers can be given a brief, calm announcement without alarming them. For the tailgating car, the correct response is to increase the space ahead so that any braking can be gradual, and to avoid brake-checking or speeding up to create a gap. The driver should signal lane changes early and smoothly if a safer lane is available, but should not weave through spray. The schedule should be rebuilt around the safe speed, not the other way round. If the car continues to tailgate, the driver should keep a steady, predictable speed and let it pass when it is safe, rather than trying to educate the other driver.