Final answer:
In welded joint designs, the anti-intrusion plate should extend to where it provides effective protection on the front bulkhead tubes, often this means covering any area exposed to potential impacts.
Step-by-step explanation:
For welded joints, the anti-intrusion plate must extend to a point on the front bulkhead tubes where it can effectively prevent the intrusion of objects into the driver's space in the event of an accident. This typically means that the plate must cover the entire section of front bulkhead tubes exposed to potential impact scenarios, ensuring complete protection. In some vehicle safety standards, this may also mean that the plate extends to the intersection with other structural elements, providing a contiguous surface that optimally distributes forces away from the driver. It is important to refer to specific vehicle design standards or competition rules, such as those from the Formula Student or SAE International, for detailed requirements, as they can provide exact measurements or proportions regarding the extension of anti-intrusion plates.