The building skin of the architecture is the next layer. Sensitive areas within a building are deeper layers requiring protection, and finally special persons information or property may require point protection or the center of the onion. The site perimeter is the first, not last, line of defense. The State Department seeks setbacks of at least 100 feet for new buildings, and even at that distance it is difficult to obtain in most urban settings. While most perimeter fences and walls are designed to discourage intruders, they are of little use against a determined person or bomb vehicle.
Designs are now available for vehicle-stopping capabilities.
However, the bomb of the future may be delivered by a moped or pedestrian, thus rendering truck bombs unnecessary. The bombing of the Murrah Federal Office Building in Oklahoma City gave birth to a federal effort to develop security standards that would apply to all federal facilities and an Interagency Security Committee has recommended their adoption as a government wide standard. During the testing of the standards, a number of state governments also reviewed the standards and applied them to several new construction projects. Consult local and state authorities for their specific applications. The process of risk assessment and security design is especially relevant in architecture of schools, hospitals, airports, office buildings, multi-family apartment buildings, etc.