The Streets module now analyzes Diverging Diamond Interchanges (DDI) as one of the most popular additions to the HCM6 procedures. Adjustments to saturation flow for the crossover movement and the DDI-specific lane utilization models have been implemented. Additional lost time to account for the off-ramp geometry are included in the adjustments for effective green time. Internal checks are performed to ensure the phasing is coded properly for the DDI movements. The DDI interchange can be modeled as part of an overall urban street facility – including for signal timing optimization.
For interchanges, the HCM dictates a series of Experienced Travel Time (ETT) results for each of the potentially fourteen movement pairs. These designations can be somewhat confusing to define as part of each interchange design type. New Interchange origin-destination graphics (including this one for DDI that is not yet in the HCM) have been added to that report to better clarify these movements as they relate to the results.
The Highway Capacity Manual Reference Guide (HCMRG) has been added to Tools. This Federal Highway Administration (FHWA) document is intended to provide simple explanations and applicable guidance for use in typical highway capacity analysis tasks. The technical approach taken within the HCMRG was intentionally not to repeat the HCM procedures themselves, but to provide key insights to critical parameters and their effects on results that would be especially useful in analysis and review.
As with all past versions, HCS7 is available for free download to all users with a current HCS support subscription and HCS 2010 data files are upwardly compatible for opening in HCS7 – Synchro files can now be imported into Streets as well. For more information, visit https://mctrans.ce.ufl.edu/mct/index.php/hcs/, or contact Bill Sampson at 352.392.0378.