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160 A suggested outline for the structure of these workshops is researchers could work to expand the knowledge base in this as follows: area and to improve ground improvement technology. Results from this research work would greatly benefit future 1. Introduction retrofit projects. 2. Objectives of this document 3. Outline of this document 7.13 Guidelines for Vehicle 4. Understanding the underlying concepts Inspections 5. Potential hazards and threats 6. Lessons learned from case studies Vehicle inspection requirements currently being employed 7. Tunnel vulnerabilities at existing facilities could be evaluated in order to develop a Incident damage potential general set of guidelines that would permit an owner to cre- Vulnerabilities of specific tunnels ate a set of appropriate vehicle inspection requirements for 8. Application guidelines the specific tunnel facility. 9. Interactive examples of application to specific tunnels 10. Conclusions 7.14 Design Criteria for New Tunnels Researchers could compile all of the new-tunnel design cri- 7.11 More Effective Broad-Based teria from various organizations into one reference source. Fire Detection Systems Currently, several organizations must be consulted for indus- During a C/B/R incident, any decision regarding the mitiga- try standards or guidelines for the design of tunnel elements. tion measures to be taken will depend on the speed and accu- These organizations include the following: racy of the detection system. However, detection systems currently in use in transportation tunnels are only capable of For tunnel structural elements: detecting smoke, temperature, and certain tailpipe exhaust con- American Concrete Institute (ACI), stituents. As discussed in Chapter 2, the introduction of C/B/R American Institute of Steel Construction (AISC), agents into the tunnel environment has become a very danger- American Welding Society (AWS), ous threat. Therefore, researchers could develop more effective FHWA, systems that can detect and identify various gases and liquids. ITA, Several national laboratories and manufacturers have been Tunnel Engineering Handbook [Ref. 24], working for some time on developing detection systems that Civil Engineering Handbook [Ref. 25], and can meet speed and accuracy requirements. In fact, several Others. prototype systems have already been deployed in transit sys- For tunnel system elements: tems and tunnels. American Society of Heating, Refrigerating and Air- The current status of detection system research and devel- Conditioning Engineers (ASHRAE), opment projects could be gathered and compiled. A program NFPA, to encourage continued development or to fill in the gaps PIARC, where research and development efforts are lacking could be Tunnel Engineering Handbook [Ref. 24], developed. Handbook of Tunnel Fire Safety [Ref. 26], Fire Protection Handbook [Ref. 27], and Others. 7.12 Ground Improvement Retrofitting Schemes 7.14.1 Tunnel Structural Elements Retrofitting existing tunnel structures to enhance tunnel resistance to blasting generally requires high and sometimes The ACI provides two important codes: Building Code prohibitive costs, and retrofitting work is often subject to sig- Requirements for Structural Concrete [Ref. 28] and Code nificant constraints from the operational standpoint (e.g., Requirements for Environmental Engineering Concrete Struc- constraints due to clearance requirements or requirements to tures (for durability) [Ref. 29]. avoid service disruption). There is, therefore, a significant The AISC provides the Steel Construction Manual [Ref. 30]. incentive for developing new retrofitting techniques to The AWS provides the Structural Welding Code for Steel address these concerns. Because information on the use of [Ref. 31] and Structuring Welding Code for Reinforcing Steel ground improvement technology is currently very limited, [Ref. 32].