At what point must vehicle traffic be stopped at a road crossing during thermite welding?

Stopping vehicle traffic at a road crossing during thermite welding is crucial for safety and effective operations. The correct point for halting traffic is prior to ignition. This is essential because the ignition of the thermite reaction generates intense heat, sparks, and molten metal that can pose significant dangers to oncoming vehicles and pedestrians. Stopping traffic beforehand ensures that the area is secure and that no one is at risk of injury from the high temperatures and flying debris associated with the welding process.

In order to create a safe working environment, it's important to have all preparations completed, including aligning the rails and applying the mold, prior to ignition. However, waiting until after rail alignment to stop traffic would not provide the necessary safety margin, as the ignition phase is inherently hazardous and requires a clear area to prevent accidents. Traffic control should therefore be firmly established before this high-risk step to ensure public safety and prevent interference during the critical ignition stage.