Distinguishing among motorized transportation modes is useful in
practice. For example, companies such as Google collect data from
travelers’ mobile phones in order to estimate the traffic speed of a
road segment. For this purpose the speed estimation system should
only use the speed reports submitted by mobile devices on cars or
buses but not those on trains. Distinguishing the train mode from
the other motorized modes enables the speed estimation system to
filter out speed reports submitted from trains.