01024789

Component

According to FHWA, the number of publicly owned vehicles reach 3,913,999 in 2003. In order to maintain a stable vehicle fleet, agencies must repeatedly make vehicle scrappage decisions because older vehicles must first retire to make room for newer vehicles. Most typically, these decisions are made based on a ranking evaluation model to select candidate vehicles for replacement. Each vehicle is given a numerical point value based on different criteria. Because these scores are assigned to each vehicle are manually, they are often subjective. The method is also deterministic, because there is no allowance for error within the course of evaluation. An alternative method to select candidate vehicles for scrappage is via an objective and probabilistic method in which the vehicle's survival probability, given its attributes are systematically calculated, while taking into consideration of the random error associated with the data. In this paper, we applied such an objective and probabilistic method to a vehicle dataset collected by the DuPage County Forest Preserve District (in the state of Illinois). A Weibull-form survival model with time-varying covariate and unobserved heterogeneity was estimated on the dataset. The results suggest that in addition to the fact that vehicle age is negatively related to the vehicle's survival probability, there are other variables that also appear equally influential. For example, minivans appear to have higher survival probability than other types of vehicles. Certain brands of vehicles have higher survival probability than others; number of road calls and repairs and using regular no-lead gasoline all appear to shorten vehicles' survival probability. The fuel type related variable is particularly worthy of noting. To authors' knowledge, no studies have examined the impact of fuel type on vehicle's survival rate. The finding of the positive impact of alternative fuel on the vehicle's survival probability certainly encourages the development and the purchase of alternative fuel vehicles.

01020180

06-1181

English

27p

2006

Transportation Research Board 85th Annual Meeting

CD-ROM

Figures (6) ; References; Tables (3)

Vehicle capacity; Vehicle characteristics; Vehicle fleets; Vehicle miles of travel; Vehicle performance; Vehicle safety

Administration and Management; Highways; Operations and Traffic Management; Planning and Forecasting; Public Transportation; Railroads; Vehicles and Equipment; I10: Economics and Administration; I90: Vehicles

Transportation Research Board Annual Meeting 2006 Paper #06-1181

TRIS, TRB

Mar 3 2006 10:36AM