Estimating the impact of parking on car ownership and commute mode choices

Researchers in commuting studies predominantly focus on movements. However, every trip starts and terminates in a place. For drivers, commuting is a journey between parking locations. They start their journey from home parking, park near work, and eventually return to home parking. Cars spend most of the day parked, with associated externalities. Drivers waste time and fuel cruising for parking in city centres and waste other drivers’ time and fuel by slowing traffic. More fuel consumption implies more carbon emissions and local air pollution. Providing off-street home parking increases house prices and reduces house affordability. Nonetheless, parking is a small part of the transportation literature and further research is needed to support a comprehensive understanding of parking and its impacts on travel behavior.

This thesis is centreed around three questions; “How does the quantity of home parking affect car ownership and commute mode?”, “How do home parking type and quantity affect car ownership?”, “How does walking time from parking location to work impact parking type choice?”. Each question is answered in a separate chapter using a discrete choice model and a sample of commuters surveyed in the New Zealand Household Travel Survey (NZHTS) in the Greater Wellington Region (GWR), New Zealand.

We find that home parking quantity strongly and positively affects car ownership and proclivity for driving. Residential parking is the most important factor in encouraging carless households to acquire a car. High home parking supply motivates households to drive more often. More car trips from suburbs means higher demand for parking downtown and highlights the relationship between home parking and work parking. More garage spaces at home noticeably motivates households to have multiple cars. The number of driveway spaces positively influences owning more than two cars. An inverse relationship exists between on-street parking demand and car ownership. For work parking, we find that walking time from public off-street parking to work significantly discourages commuters from choosing public off-street parking. Walking time from an on-street parking to work is also a significant disincentive for choosing On-street parking. The cost of on-street parking is important, followed by the number of on-street parking spaces. Elasticities show that the motivation of drivers to change parking type is close to their willingness to choose non-driving modes, if any parking features change. This similar willingness indicates a potential for achieving lower car use through parking restriction and improving non-driving modes.

This research contributes to the home parking literature by considering residential location as a choice that is interrelated with car ownership and mode choice. We study commuters who could live and work anywhere in a region (GWR) with a diverse range of socioeconomic characteristics, parking features, and traffic conditions, in order to give results that are more realistic and comprehensive. We mitigate the endogeneity between car ownership and home parking using novel instrumental variables for home parking. Our measure for on-street parking carefully considers parking competition and quantity. Commute length is measured as commute time to better represent commuters’ perception of commute length. For work parking, we consider mode choices and parking alternatives simultaneously, and use novel demand-based measures for parking features.

We expect the findings of this research will contribute to a better understanding of how parking arrangements in cities can affect commuting patterns, and how parking policies can impact urban design, land use and transport outcomes.