A lockage operation consists of a vessel entering the lock chamber, having the water level raised or lowered as needed, and then exiting the chamber.
The data includes 70,180 individual lockages in our study section and shows a large variability in the distribution of lockage times.
Smith, Sweeney, and Campbell (2009) identify calendar year 2000 as the most representative year of normal UMR operations in our lockage data because that year was relatively unaffected by extraordinary system events such as extended lock closures, and it experienced relatively typical weather, water flow, and other operating conditions.
From careful analysis of the detailed lockage data for the baseline year, we identified 4,970 itineraries for Double and Single Tows, with the origin and destination pattern shown in table 3.
The vessel-processing times at the individual locks and transit times through the pools are distributed log-normally in the model, with means and variances varying monthly by vessel type, operational lockage type, and direction of movement.
the number of lockages, lockage times, pool transit times) we refer the reader to Smith, Sweeney, and Campbell (2009).
To further explore the impact of including shippers' choice in the model, we examine system performance under increasing traffic demands in conjunction with the implementation of three proposed UMR congestion mitigation measures (National Research Council 2004): (1) amended vessel scheduling at locks via a "fastest expected lockage time" policy (FLT), (2) providing helper boats at locks in conjunction with FLT scheduling (HLP), and (3) construction of larger new locks (NEW).
These helper boats decrease the lockage time for each Double Tow by approximately 15 minutes (US Army Corps of Engineers 2004).
With new 1,200-foot locks, all lockages become single cut lockages and lockage times drop dramatically for tows that are currently processed in a double cut lockage.
Table 1/Annual Lockages, Percent of Total, Mean, and Standard Deviation of Lockage Times at UMR Locks 20-25 Lock Vessel Croup Lockages Lockages Mean Lockage Time (min.
Currently, the Corps operates each lock under a modified firstin, first-out local operating policy called RECPRIO that gives locking priority to recreational and governmental vessels by requiring that these noncommercial vessels wait for no more than three commercial vessel lockages before moving to the front of the queue.
Fortunately, the Corps does collect some data on the vessel lockages at each lock.