Application of Machine Learning to Child Mode Choice with a Novel Technique to Optimize Hyperparameters.

Travel mode choice (TMC) prediction is crucial for transportation planning. Most previous studies have focused on TMC in adults, whereas predicting TMC in children has received less attention. On the other hand, previous children's TMC prediction studies have generally focused on home-to-school TMC. Hence, LIGHT GRADIENT BOOSTING MACHINE (LGBM), as a robust machine learning method, is applied to predict children's TMC and detect its determinants since it can present the relative influence of variables on children's TMC. Nonetheless, the use of machine learning introduces its own challenges. First, these methods and their performance are highly dependent on the choice of "hyperparameters". To solve this issue, a novel technique, called multi-objective hyperparameter tuning (MOHPT), is proposed to select hyperparameters using a multi-objective metaheuristic optimization framework. The performance of the proposed technique is compared with conventional hyperparameters tuning methods, including random search, grid search, and "Hyperopt". Second, machine learning methods are black-box tools and hard to interpret. To overcome this deficiency, the most influential parameters on children's TMC are determined by LGBM, and logistic regression is employed to investigate how these parameters influence children's TMC. The results suggest that MOHPT outperforms conventional methods in tuning hyperparameters on the basis of prediction accuracy and computational cost. Trip distance, "walkability" and "bikeability" of the origin location, age, and household income are principal determinants of child mode choice. Furthermore, older children, those who live in walkable and bikeable areas, those belonging low-income groups, and short-distance travelers are more likely to travel by sustainable transportation modes.

Children's Access to Non-School Destinations by Active or Independent Travel: A Scoping Review.

BACKGROUND: Children's access to non-school destinations is important for their well-being, but this has been overlooked in transport planning. Research on children's access to non-school destinations is growing, and there is a need for a comprehensive overview, examining both quantitative and qualitative studies, of the existing evidence on places that children access by active or independent travel. OBJECTIVES: Identify and summarize quantitative and qualitative research on the topic of active or independent travel to non-school destinations for elementary aged children (6 to 13 years old). METHODS: Papers published in English between 1980 and July 2021 were sourced from: (i) Web of Science Core Collection; (ii) PubMed; and (iii) APA PsycInfo. Three relevant journals related to children and transport were hand searched: (i) Children's Geographies; (ii) Journal of Transport & Health; and (iii) Journal of Transport Geography. The search was limited to peer-reviewed articles published in English between 1980 and July 2021. Covidence, an online software platform for systematic reviews, was used to organize articles during the title and abstract screening stage. PRISMA-Scr is applied for reporting. RESULTS: 27 papers were retained from an initial 1293 identified peer-reviewed articles. The results reveal that children in different geographies travel unsupervised or by active modes to places that support different domains of their well-being such as a friend or relative's home, local parks or green spaces, recreational facilities, and different retail locations (e.g., restaurants). There is evidence that children's ability to reach certain places is constrained, likely due to safety concerns or environmental barriers. CONCLUSIONS: Research on children's diverse destinations is relatively limited as compared to trips to school. Various methodologies have been applied and can be combined to completement each other such as objective GPS tracking and subjective surveys on places children would go if they were available. Future research should clearly report and discuss the non-school destinations that children access to better inform transport planning and policy for all aspects of children's lives.