Angela Jannini Weissmann

Computerized Equipment Replacement Methodology

The Texas Department of Transportation (DOT) owns and maintains an active fleet inventory of approximately 17,000 units and replaces about 10% of them annually. Any methodology that can improve Texas DOT’s replacement procedures could potentially save millions of dollars. Private and public agencies do not routinely use life-cycle cost as a replacement criterion because the only way to automate inspection of thousands of life-cycle cost histories has been to define an acceptability threshold for annualized costs. Most fleet managers consider this practice too inaccurate. The most relevant information provided by a lifecycle cost graph is its trend. Units whose life-cycle costs have been increasing longer or at a faster rate should have higher replacement priority. The trend score concept allows a computer to mimic replacement decisions made by a person visually inspecting a series of life-cycle cost histories. A new economically sound methodology for assisting with equipment replacement at Texas DOT is presented. This new method takes full advantage of Texas DOT’s comprehensive equipment operating system database, can prioritize the units on the basis of comparisons among all units within any desired class of equipment, and uses life-cycle cost trends as a replacement criterion. This methodology was implemented through the Texas Equipment Replacement Model, a menudriven software that allows the fleet manager to efficiently apply the methodology.

Traffic Simulation at International Ports of Entry: El Paso-Mexico Case Study

Since the implementation of the North American Free Trade Agreement (NAFTA) in 1993, international commercial traffic has grown significantly. Texas has been the largest port of entry for trade at the U.S.-Mexico border since 1994, accounting for approximately 75 percent of the trade. Under NAFTA, FHWA predicts that trade through Texas could increase up to 120 percent in the coming years. Texas has 18 border sectors with Mexico, many of which have congestion primarily caused by ineffective interaction among inspection procedures and traffic management or lack of adequate transportation planning. A simulation model, developed using a general-purpose industrial engineering simulation package, can help determine the best alternative for preventing congestion at the ports of entry and the associated traffic operation effects on the road network adjoining the international bridges, while yet maintaining an adequate inspection of commercial trucks. A case study of the Ysleta-Zaragoza Bridge in El Paso, Texas, is presented. The simulation shows that the traffic flow at the Ysleta-Zaragoza Bridge is efficient with the current infrastructure and traffic operations. However, the expected future increase in traffic volume will generate a spill-back into major freeways close to the bridge. A proposed solution to this problem is presented.