If the places we visit are within cycling distance, do we drive less? Is it really accessibility that is stopping us from using our bike to visit work, the supermarket, doctors and schools or is it something more such as behaviour or convenience? This is the question I wanted to answer through research for my masters, comparing transport accessibility to vehicle kilometres travelled (VKT).
I used accessibility modelling and a scoring system to understand who is able to reach essential destinations such as supermarkets, workplace, doctors, hospitals and schools within a cyclable distance. In Christchurch, for example, the closer you are to the central city, the better cycling accessibility you have, as shown in the figure below.
Comparing the above to the product of VKT and car ownership (see figure below) shows a strong correlation with accessibility (R2=0.56), meaning people drive less as their accessibility improves.
Even though there’s a strong relationship between better accessibility and lower VKT this can be improved through transport-related policies such as cycling infrastructure provisions and encouraging high-density development, although these may be ineffective in high accessibility/high VKT areas. The analysis raises questions such as: are people making shorter trips in highly accessible areas? and what are the reasons for outlying results ? (e.g. the Avon-Loop, Edgeware, Merivale, Paparua and Trent Ladbrooks. These are likely to be explained by factors beyond accessibility, such as comfort and convenience.
Although there is plenty of opportunity for further investigation, what can be concluded is: being close to destinations will mean you are less likely to drive as far, either making fewer or shorter car trips. By inference, this suggests that people who live in more accessible locations do or could cycle more if the right external conditions are provided, e.g. cycle infrastructure and culture, although further research would be required to further explore this.
If you’re interested in reading the whole dissertation, you can find it here: https://researcharchive.lincoln.ac.nz/handle/10182/11426
Blog written by Fraser Dixon, Graduate Transportation Planner