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Problem 6
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Problem 6 Discussion - Page 1 of 1

ID# C2060D1

Problem 6: Route 146 Arterial Study 

There are several important points to make based on this problem. The first is that HCM analyses prepared us quite well for the network analysis. TRANSYT-7F was able to improve the performance of the system (delay-wise) by only about 8%, when it optimized the signal timings. In terms of assessing the performance of these intersections, we learned a lot from the HCM analyses that helped prepare us for the TRANSYT-7F investigation.

The second observation is that the way the HCM treats these intersections is very similar to the way they are treated in TRANSYT-7F. The two analytical methods expect very similar inputs, treat the problem in similar ways, and produce similar outputs. If you review the Help screens and text in TRANSYT-7F, you will find numerous references to the HCM. This indicates a significant consistency between these two tools, providing some assurance that findings obtained from the HCM will be similar to those from TRANSYT-7F, and vice versa.

The one major difference between the HCM and TRANSYT-7F is that the capacities of the saturation flow rates are derived by the HCM, whereas they are inputs in the case of TRANSYT-7F. Oftentimes, it helps to do the HCM analyses first and get credible saturation flow rates for the various lane groups before starting a TRANSYT-7F analysis. That will increase the consistency of the results you obtain.

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