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37 7 6 5 Frequency 4 3 2 1 0 20,000 30,000 40,000 50,000 60,000 70,000 More ATCS Installation Costs per Intersection (US $) FIGURE 12 Histogram of ATCS installation costs. however, the scatter of the data points is reduced. This chart hardware, and software costs) for ATCS and non-ATCS sig- shows that when it comes to the costs of the physical mainte- nals. A variety of answers were collected from respondents: nance, ATCSs are more efficient than conventional traffic sig- from costs of maintaining an ATCS being 10 times lower than nal systems, which is the opposite of a widely accepted notion a non-ATCS costs to non-ATCS costs being 4 times lower that ATCSs are expensive to maintain (especially communi- than ATCS costs. On average, the ATCS agencies found that cations and detection). maintaining "optimal" signal timings under an ATCS accounts for only 75% of what is spent to maintain comparable signal The other components of costs for maintaining an ATCS timings under non-ATCS signals. operation include consulting costs and the costs of maintain- ing ATCS hardware and software. Although there is a notion that once an ATCS is set up there is no need for re-timing EVALUATION STUDIES traffic signal timing plans, there are some costs of reconfig- uring ATCS parameters. These costs can be significant owing Evaluation studies that compare the effectiveness of a pre- to inadequate in-house expertise to adjust ATCS parameters to ATCS traffic signal system with the effectiveness of the meet new operational needs. Most ATCS agencies have diffi- ATCS usually follow any new ATCS deployment. Most of culties comparing estimates for the per-intersection annual the time (in 53% of the cases) ATCS users hire outside costs of maintaining optimal signal timings (e.g., consulting, consultants to measure improvements in traffic operations 100.00% 90.00% 80.00% Percent of Annual Budget for ATCS 70.00% y = 0.6459x + 0.0232 R2 = 0.7269 60.00% 50.00% 40.00% 30.00% 20.00% 10.00% 0.00% 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% Percent of Intersections under ATCS FIGURE 13 Correlation between ATCS shares in budget and operations.