Dynamax is a road side based system using the SPECIALIST control algorithm and inductive loops. Dynamax field tests showed that moving jams can be effectively resolved by dynamic speed measures [1,5]. This paper focuses on Dynamax In Car, which extends the road side infrastructure with a V2I cooperative approach. V2I cooperation is used to detect an emerging jam earlier and more accurately, so that a smaller speed measure can be set to resolve it and larger moving jams can be resolved within the available road length. The detection performance is analyzed through simulation and found to improve already with a very low penetration rate. An additional road side detection system is also analyzed that is independent of the penetration rate and provides the best detection performance.