Drivers must maintain a constant speed when passing and reentering the lane in front of trucks or buses since they require:

Maintaining a constant speed when passing trucks or buses is critical because these larger vehicles typically have longer stopping distances compared to smaller cars. This means that if a driver slows down significantly while trying to pass, it could lead to a situation where the truck or bus may not be able to stop in time if something goes wrong. Trucks and buses are heavier and require more time and distance to decelerate, making it essential for the passing driver to keep a steady speed to ensure safety for everyone on the road.

The other options, while related to driving safety, do not accurately address the key reason why maintaining speed is crucial when passing larger vehicles. The focus on longer stopping distances highlights the need for drivers to be assertive and consistent while executing maneuvers around trucks and buses.