Abstract
Recently, research for full speed range Adaptive Cruise Control (FSRA)
function has been promoted. However, there is a concern that the use of FSRA function may
lead to a decrease in driving awareness while following another vehicle. This study examined
the conceptual design of the control range and warning of FSRA function and the effect of
FSRA function on driver behavior.
1) We studied the specification of the control range and warning of FSRA to maintain driving
awareness. We examined driver braking while following another vehicle and analyzed at what
point the driver wants to brake in relation to TTC (Time To Collision). The results were
applied to the specification of the warning of FSRA.
2) We investigated the influence of FSRA on driver braking response on road.
An experimental vehicle equipped with FSRA was prepared based on the above specification.
We examined the driver´s car-following behavior with and without FSRA on metropolitan
expressways. Ten drivers participated (aged between 25 and 56). The results showed that
there was no significant difference in TTC at the start of braking behavior against the
decelerating preceding vehicle, when comparing the cases with and without FSRA control.
According to the test, there was no difference between driving with and without FSRA control.
Driver braking behavior against a cut-in vehicle with and without FSRA control indicated
similar results. It showed that the use of FSRA function did not lead to a decrease of driving
awareness.
3) We investigated the reduction of driver workload.
We analyzed the frequency of driver braking on Route 23 (a highway) with and without FSRA
control and the driver´s subjective workload by using the NASA-TLX method.
Our results indicate that the use of FSRA reduced driver´s braking frequency thus, reducing
driver´s workload.
In conclusion, 1) the control range and the warning of FSRA were important for maintaining
driving awareness; 2) there was no evidence of decreased driving awareness due to the use of
FSRA; 3) application of FSRA led to a reduction of driver workload.
Keywords - Driver behavior, driver workload, FSRA, ACC, time to collision