Truck Scheduling for Ground to Air Connectivity

Problem

A critical link in the overnight package business is the on-time arrival of trucks at airport terminals. Truck delays can delay the package sorting and transfer process, which can in turn delay aircraft departures from the local terminal, as well as aircraft departures from hub terminals that depend on timely aircraft arrivals. The sorting process at the origin airport is a particularly critical step, as it is susceptible to random delays in the arrival of work, and because it demands relatively large investments in facilities and labor.

This research models the sorting process at the airport terminal and the effects of truck arrival time on the completion of the sort. Predictions are provided for expectation and standard deviation of arrived work. From these predictions, performance measures are developed for sort end-time and sort starvation (the decrease of truck arrivals to be sorted until the sorting process is idle). Particular attention is given to scheduling the start time for the sorting process, to balance a trade-off between maximizing sort productivity and minimizing the end-time of the sort. The methods are being implemented as a Web-based scheduling tool.

This research is based on a project that was completed in cooperation with the two largest private express package companies in the United States: Federal Express and United Parcel Service.

Findings

The models developed in this paper for evaluating performance are being implemented as a Web-based tool. Multiple users, located at different sites, can enter and edit data on planned schedules and can adjust the data on a daily basis to reflect current conditions. The tool produces graphs of expected cumulative arrival and completion of work and also indicates when there is substantial likelihood of "starvation."

The tool also provides "what if" capability so that the effects of a change in schedule can be evaluated. For example, the user may alter the departure time to see whether the change is likely to cause "starvation" and a delay in the completion of the sort. This provides some guidance in whether a truck should be released immediately or held over for late shipments.

Lastly, the tool provides a means for information sharing among multiple sites.

An added feature under development is a real-time forecasting capability. This will entail monitoring current traffic conditions and incorporating the conditions in predictions for travel time allowing the user to forecast the arrival of work and more accurately predict whether starvation will occur.