  Time sharing between activities remains an indispensable part of everyday
activity pattern. However, the issue has not yet been fully acknowledged within
the existing time allocation models, potentially resulting in inaccuracies in
valuing travel time savings. Therefore this study is aimed at addressing this
gap by investigating the potential impact of introducing time sharing within
such a framework, as well as factors determining it as represented by travel
activities. In doing so, time constraint in the time allocation model of Small
was modified to enable sharing the same time interval between different
activities. The resulting expression indicated that such an augmentation could
lead to lower estimates of value of time as a resource. On the other hand,
empirical research based on the data from the National Passenger Survey 2004
used for calibrating cross-nested logit model indicated a number of factors
affecting the choice of travel activities. It was discovered that significant
include possession of equipment allowing particular activities, e.g. newspaper,
paperwork or ICT devices, companionship, gender, length of the journey,
frequency of using the service, possibility of working on the train, journey
planning in advance, first class travel, termination of the trip in central
London, peak-time travel and availability of seating.
