Calling while driving poses a severe safety risk. When more than two people are involved in a call - a conference call - this risk increases even more. Intelligent vehicles could offer support systems that ease the cognitive burden of such a multiparty calls. We explore the possibilities of such advanced driving assistant systems (ADAS) in two ways: first, we investigate object-based spatial audio where each remote caller is modeled as a distinct audio source. Second, we apply a non-intrusive ambient stereoscopic 3D (S3D) visualization that indicates the current speaker and its location. In a between-subject design driving simulator study (n=56), we assess workload, user experience and driving performance. Surprisingly, we found no positive effect of object-based audio. However, we present evidence how a supporting visualization might lower situational stress and increase the system’s dependability. We conclude that a supportive and intelligent stereoscopic visualization is a promising candidate for enhancing multiparty conference calls while driving.