The Two-Way Stop Control (TWSC) module has been completely rebuilt in the latest software architecture to provide a redesigned user interface for inclusion in HCS 2010 Release 6.70. This update now implements the procedures described in Chapter 19 of the HCM 2010. The new architecture allows for breaking data entry into smaller portions using sliding screens, including classic mode with one scrollable screen as an option in Full View.

Six-Lane Major Streets

One of the main reasons for updating this chapter was to accommodate intersections with three lanes in each direction on the major street. The principle modification to model these intersections was to provide appropriate critical and follow-up headway values for the various movements operating under these conditions. The lane configuration within this module will now allow up to six thru lanes on the major street to expand the results for these intersections.

Major-Street U-Turns

Especially with six-lane major streets, but also affecting those with four lane, the U-turn movements had to be included in these analyses. Conflicting flows and headway times were defined for computing capacity with impedance considered for ultimately calculating delay to determine level of service for these movements in the updated procedure. U-turns are now included in the lane configuration and demand coding within the software to generate these results.

Upstream Signals

The procedure defined to model the effects of upstream signals on the conflicting flows and the resulting capacity for the TWSC analysis has been replaced. Instead of computing the proportion time blocked within the TWSC method, the more comprehensive procedure defined within HCM 2010 Chapter 17 for Urban Streets. Modeling the adjacent signalized intersection(s) in the Streets module with the TWSC intersection coded as an access point generates this value for use in the TWSC analysis.

Short-Lane Modeling

The method has always modeled delay to Rank 1 (major-street thrus and rights) created by left-turning vehicles with no exclusive lane. The HCM 2010 procedure adds the ability to model this delay when the left-turn lane is insufficient to accommodate the predicted queue, essentially creating queue spillover.

HCS 2010 Release 6.70

McTrans is completing the final beta testing for this module now and hopes to release it in May. An announcement will be emailed to all registered users and posted on the web site.  For more information, contact Bill Sampson, director, McTrans at bsampson@ufl.edu.