  Traffic jams occurring on highways cause increased travel time as well as
increased fuel consumption and collisions. Traffic jams without a clear cause,
such as an on-ramp or an accident, are called phantom traffic jams and are said
to make up 50% of all traffic jams. They are the result of an unstable traffic
flow caused by human driving behavior. Automating the longitudinal vehicle
motion of only 5% of all cars in the flow can dissipate phantom traffic jams.
However, driving automation introduces safety issues when human drivers need to
take over the control from the automation. We investigated whether phantom
traffic jams can be dissolved using haptic shared control. This keeps humans in
the loop and thus bypasses the problem of humans' limited capacity to take over
control, while benefiting from most advantages of automation. In an experiment
with 24 participants in a driving simulator, we tested the effect of haptic
shared control on the dynamics of traffic flow, and compared it with manual
control and full automation. We also investigated the effect of two control
types on participants' behavior during simulated silent automation failures.
Results show that haptic shared control can help dissipating phantom traffic
jams better than fully manual control but worse than full automation. We also
found that haptic shared control reduces the occurrence of unsafe situations
caused by silent automation failures compared to full automation. Our results
suggest that haptic shared control can dissipate phantom traffic jams while
preventing safety risks associated with full automation.
