Problem 6: Route 146 Arterial Study 

Discussion
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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