Modular design of fatigue detection in naturalistic driving environments.

•A scalable modular design approach is considered to build a system using a Bayesian combiner and a particle swarm optimiser (PSO).•The proposed system is flexible in terms of the available input data and more robust against losing one or more data sources.•A new modification is applied to the Bayesian combiner to enable the particle swarm optimiser algorithm to work in conjunction with the combiner.