The study consists of four separate experiments conducted in the VTI driving
simulator. The common theme was to investigate how driver behaviour and
traffic safety are influenced when the driver attends to another technical
device while driving. The experiments were concerned with handsfree or
handheld mobile phone conversation and dialling, receiving mobile phone SMS
messages and watching a DVD film (the latter two being minor pilot
experiments). In three of the experiments (mobile phone conversation, SMS,
DVD) the participants drove a route which led through urban and rural
environments, ranging from 90 km/h rural to 50 km/h urban environments. The
urban environments differed in complexity (three levels). The driving
distance was about 70 km. The dialling experiment used a rural environment
with a speed limit of 110 km/h. The driving distance was about 15 km. In the
main experiment dealing with mobile phone conversation, a number of driving
performance measures were analysed: driving speed, variation in lateral
position, deceleration, brake reaction time, headway, time to collision, etc.
PDT (Peripheral Detection Task) was used as a measure of mental workload.
Mobile phone conversation was found demanding in terms of mental workload. It
also had effects on driving. Most effects were quite similar for the two
phone modes (handsfree, handheld). Impaired reaction time performance was
demonstrated in one of the situations for handheld mode. However, effects
were found which could be interpreted as attempts to compensate for the
increased workload caused by the mobile phone conversation: speed was reduced
(more so for handheld than for handsfree mode), and time and distance headway
increased. In spite of these compensatory behaviours, mental workload was
still markedly increased by phone use. In the SMS experiment the participants
braked later in one situation when reading the SMS message. No other effects
were found in this minor experiment. In the DVD experiment, mental workload
increased when watching the film, although this was compensated for to some
extent by the increased distance headway to a lead vehicle. No compensation
in terms of reduced driving speed, however, was apparent in this experiment.
In the dialling experiment negative effects on traffic safety were evident
from the larger variance of lateral car position during the dialling task for
the handsfree phone mode. The mental workload also increased with the
dialling task. Compensation in terms of reduced driving speed was apparent
for both phone modes. Other aspects of mobile phone use while driving still
remain to be analysed in more detail, such as starting or finishing a call,
looking for a phone number to dial, mishaps like dropping the phone, etc.
Linköping: Statens väg- och transportforskningsinstitut., VTI meddelande 969A , 2004.
English, Sweden, Mobile, Telephone, Driving, Simulator, Driver, Behaviour, Attention, Driving aptitude, Stress, Safety