6 JANUARY/FEBRUARY 2018 • FOGHORN FOGHORNFOCUS: SALES & MARKETING D o you understand what causes fluctuations in your ferry system ridership? Have you been asked to forecast vehicle or passenger growth for a terminal improvement or new vessel design? Tasked with designing a replacement ferry for Skagit County, Seattle naval architecture and marine engineering firm Glosten combed through forty years of ridership data to answer these questions. This article will describe our method and findings, and suggest data visualization techniques that may help improve your understanding of past and future ferry ridership. In the summer of 2017, Glosten was selected by Washington State-based Skagit County to design a replacement vehicle/passenger ferry for service to Guemes Island. This small rural island is home to a tight-knit community with 750 full-time residents and a fluctuat- ing summer population of roughly 2,000. Naturally, summer weekends and holidays have the highest ridership demand, but weekly commuter traffic throughout the year makes up the bulk of ridership on an annual basis. The What’s Hiding in Your Ridership Data? “Operators should not underestimate the importance of keeping detailed, organized electronic ridership data.” By William L. Moon, III, PE, Glosten Associates from 1980 through 2016. Prior to 2000, the records contained only annual passenger and vehicle totals, but records after that date included the number of passengers and vehicles on each crossing, as well as the mainland departure time. The richness of the latter dataset enabled Glosten to examine seasonal, weekly, and daily demand patterns, as well as hourly service and utilization rates. This level of detail was helpful not only in sizing Skagit County’s new ferry, but also in planning shoreside facilities upgrades. Vehicle ridership data from 1980 to 2016 is shown in Figure 1. Growth is fairly steady up to the early 2000s, but a distinct drop after 2002 had many puzzled. Previous forecasting attempts (shown in dashed lines) relied on the generally linear growth trend from 1980 to 2002. While this method was not conceptually incorrect, it did not account for the reduction in ridership from 2002-2016, which is more than a random fluctuation. It became clear that uncovering the factors influencing ridership during that time would be essential to accurately forecast the re- placement vessel’s ridership. Ridership Fluctuation – Initial Hypotheses Skagit County’s population size appeared to be strongly correlated existing ferry, the M/V Guemes, went into service in 1979 and has met the needs of the county. It is a double-end- ed steel ferry that holds 21 vehicles and 100 passengers, with an open car deck and an offset deckhouse. Preparing for Future Demand In order to recommend a new ferry capacity, Glosten first needed to estimate future ridership demand. To this end, Skagit County provided electronic ridership records dating Let‘s talk about it Is Electric Right For You? Torqeedo Inc. 171 Erick Street, Unit A - 1 Crystal Lake, IL 60014 T +1 (815) 444 8806 usa@torqeedo.com www.torqeedo.com