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35 TABLE 12 MEDIA FOR PEER-TO-PEER COMMUNICATION Communication Media Percent of Agencies Twisted pair 43 Fiber optic 41 Telephone line 20 Wireless 7 Microwave 2 Other media 5 Does not need any peer- to-peer communications 16 Note: Total percentage exceeds 100 because some of the interviewed agencies deploy multiple types of communication media at various intersections under their jurisdiction. in ATCS operations. Table 12 shows the percentages of vari- those for conventional traffic-actuated control systems. Most ous media types used by interviewed ATCS users for their of the ATCS users are satisfied with the way their system han- peer-to-peer communications. dles minor detector malfunctions and reports the major detec- tor malfunctions. Early problems with ATCS hardware, which Overall, ATCS users do not find that communications for was incompatible for local controllers (primarily for early their ATCSs are much more demanding than communications installations of international ATCSs), are mostly gone. ATCS for conventional traffic control systems. The majority of the users still sometimes struggle with handling ATCS-specific respondents (72%) find that their communications for ATCSs hardware primarily owing to a lack of operational knowledge, function similar to other traffic control systems. Sixteen per- which in turn indicates a lack of proper training. Although cent of the respondents indicated that they have more problems most of the users find their ATCS software to be user-friendly, with communications for the ATCS than with communica- there is a notion that the friendliness of the software can be tions for their regular systems, whereas 12% of the respon- significantly improved. Most of the ATCS users do not find dents believe that the opposite is the case. that ATCS communications cause more problems than the communications of conventional traffic control systems. Still, SUMMARY communications costs are one of the major operational costs for ATCS users and communications problems may take sig- This chapter identified system requirements for ATCSs nificant amounts of their time and resources. The next chapter and described how ATCS users perceive those requirements. reports on the implementation costs and benefits of ATCS Detection requirements for ATCSs remain slightly higher than deployments.