| Summary |
Tsu-Hurng Yeh,2007.01
Department of Transportation Technology and Management National Chiao Tung University
Vehicle duration variables such as holding duration and scrappage age are crucial for transportation planning and management, environmental protection, and traffic safety improvements. Most studies on vehicle duration have been focused on automobiles, but comparatively little has been noted on motorcycles. However, it is valuable to put much emphasis on motorcycle duration studies due to the high ownership rate for many Asian countries and also the ownership increase in some European countries.
Some weaknesses in research design and methodology for the previous motorcycle duration studies have been identified. These drawbacks originate mainly from the difficulties and elevated cost in establishing qualified duration data. In this study, a combination of the MOTC’s sampling survey on motorcycle usage in 2000 with the corresponding registration information in the Vehicle Registration System (VRS) was developed. Via a four-more-years observation period, three different measurements for duration variables ─ motorcycle holding duration, scrappage age, and age of second-hand motorcycles purchased ─ can be observed. A Cox regression model was applied and two competing risks for ending motorcycle holding by disposal or by transfer were also estimated. However, around 11.8% of the samples have been discarded but not been registered in the VRS at the observation start. To reduce the bias from part of these censored data, we further applied a split-population duration model to correct the heterogeneity of holding duration and scrappage age.
The results indicated that a used motorcycle purchased, lower engine size, higher running mileage and maintenance cost, less motorcycle and less car fleet size in a household reduced both the holding duration and scrappage age; but in contrast, older owners, less monthly income, and a motorcycle registered in Greater Taipei extended the holding duration and scrappage age. Aggregate socioeconomic predictors such as higher unemployment rate and lower consumption propensity also increased the holding time and overall life span of district’s motorcycles. In addition, better emissions inspection performance of a district shortened the age of motorcycles being scrapped. The estimated split-population parameter showed that around 21% of observations for the holding duration and 47% for the scrappage age from the registration records had been prolonged censoring at the end of observation. Some policy implications connected with old motorcycles, emissions inspection, and vehicle registration system were raised and limitations about research design and modeling issues were also discussed. |
