What encourages people to carpool? An evaluation of factors with meta-analysis

Non-household carpools (where two or more commuters from different residences travel together in the same private vehicle) bring public benefits. To encourage and incentivise it, transport practitioners and researchers must understand its private motivations and deterrents. Existing studies often report conflicting results or non-generalisable findings. Thus, a quantitative systematic review of the literature body is needed. Using meta-analysis, this study synthesised 22 existing empirical studies (representing over 79,000 observations) to produce an integrated review of the carpooling literature. The meta-analysis determined 24 non-household carpooling factors, and their effect sizes. Factors such as number of employees ( $$\bar{r} = 0.42$$ r ¯ = 0.42 ), partner matching programs ( $$\bar{r} = 0.42$$ r ¯ = 0.42 ), female ( $$\bar{r} = 0.22$$ r ¯ = 0.22 ) and fixed work schedule ( $$\bar{r} = 0.15$$ r ¯ = 0.15 ) were found to have strong effects on carpooling while judgmental factors (such as the motivation to save costs) only exhibited small influence ( $$\bar{r}