Modeling Car Sharing and Its Impact on Auto Ownership: Evidence from Vancouver and Seattle
Car sharing is a relatively recent phenomenon but an increasingly important phenomenon in understanding urban household travel behavior. TransLink, the agency responsible for carrying out regional transportation planning for metropolitan Vancouver, British Columbia, and the Puget Sound Regional Council (PSRC) the MPO for metropolitan Seattle, have started investigating this issue. Their recent travel surveys asked the question of all households whether anyone in the household was a member of a car sharing service (not merely using a ride sharing app such as Uber or Lyft) In addition to investigating the impact of car sharing membership on household auto ownership, these surveys provide insight into whether car sharing services lead to a net increase or decrease in motorized travel at the household level. Two models are investigated in this paper. First, a conventional model of household auto ownership is estimated with car sharing treated as an exogenous input, along with a stand alone model of car sharing membership. This is followed by a more complex household mobility model that is outlined in the paper (a simultaneous model of household car sharing and auto ownership) which only would make sense in the context of an activity based model or at least a model with a population synthesizer. In terms of model results, income is a major predictor of car sharing membership and auto ownership. As expected, the presence of seniors in household and proximity to car sharing lot have the biggest impact on car sharing membership. These variables also impact auto ownership directly, though we find number of workers in the household to play an even larger direct role in auto ownership. As far as the overall implications emerging from these models, we recommend that auto ownership models be refined to take car sharing membership and ideally transit pass holding into account. In most cases, a series of sequential models will be more feasible than estimating and implementing the simultaneous household mobility model outlined in this paper. Given the strong growth of car sharing in the Pacific Northwest, as well as across North America, we recommend that further research into car sharing membership be carried out, and this of course also means monitoring the growth in usage of traditional car sharing services, as well as the car ride services, which have been transforming the urban transportation system in recent years.