Does driving with ACC means safer speed and headways?

In the past decade a number of studies about the effects of ACC on driving behaviour have been reported. However, different studies obtained different results, which made difficult to come up with a general conclusion about the effects ACC have on driving behaviour and road safety in general. Therefore, in this study, a meta-analytic approach was used to integrate different results of various driving simulator studies about the effects ACC on mean driving speed and mean time headway. The results of this study indicate that the effect of ACC seems to be dependent on the type of ACC used in a particular study. When driving with types of ACC that could take over more of the driving tasks and could provide more support to the drivers (allocate more tasks to the system in comparison to other types of ACC), drivers change their behaviour in the riskier direction by increasing their driving speed and at the same time decreasing their headway.