What should be done if the fuel level is at or below 1/2 tank?

Refueling immediately when the fuel level is at or below half a tank is essential for maintaining safety and operational efficiency during a trip. Driving with insufficient fuel can lead to situations where a vehicle might run out of gas, increasing the risk of stranding passengers and creating potential safety hazards. It also limits the flexibility of the route, as the driver might have to seek out fuel stations during a scheduled route, which could cause delays.

Furthermore, keeping the fuel tank above half full helps guard against condensation in the tank, which can lead to water accumulation and potential engine problems. This preventive measure ensures smooth operation and reduces the risk of breakdowns related to fuel issues.

The other options suggest actions that could compromise safety and operational effectiveness. Completing a trip before refueling could lead to running low on fuel and potentially interrupting service. Noting the fuel level and proceeding cautiously does not adequately address the risk of running out of fuel, and leaving the yard with less than a half tank doesn't meet the recommended safety standards for operation. Refueling immediately ensures that the vehicle is always ready for the journey ahead.