This thesis is assessing the effects of (Cooperative) Adaptive Cruise Control using microscopic and mesoscopic simulations in Aimsun. The Gipps car-following model is manipulated in such a way that it represents (C)ACC driving behavior to a satisfactory extent. A simulation network of a part of the A15 highway containing the junctions Ridderkerk, Vaanplein and Benelux is used to assess network-wide and bottleneck specific traffic flow effects of increasing market penetration rates of (C)ACC. Microscopic simulations showed that the results of increasing market penetration rates of ACC range from negative to positive effects, while increasing market penetration rates of CACC generally provide positive effects. Additionally, traffic flow effects of increasing penetration rates of (C)ACC at on-ramps, weaving sections, lane drops and bottlenecks where extreme braking is applied, have been assessed. At on-ramps, ACC systems generally have a negative to no effect, while CACC systems show positive effects. At weaving sections, increasing penetration rates of (C)ACC could either have a positive or negative effect, depending on the lay-out and characteristics of the weaving section. At lane drops, (C)ACC systems generally have a negative to no effect. At bottlenecks where extreme braking is applied, (C)ACC systems have a very positive effect, since these systems have a homogenizing effect on traffic flow. Additionally, at road sections at or near capacity, (C)ACC systems were found to have a homogenizing effect on traffic flow. Although the microscopic simulation showed reasonable and credible results, some improvements to model (C)ACC more effectively could still be made. For example, by including the possibility to activate and deactivate (C)ACC systems at certain times or locations in the network. Furthermore, mesoscopic simulations in Aimsun were performed in order to find out whether it is possible to obtain similar results as found in microscopic simulations. The relation between mesoscopic and microscopic simulations in Aimsun is still unclear when fixed time headway settings are applied, which indicates that further research on this topic is necessary. In general, mesoscopic simulations could be used as an indication on the traffic flow effects of (C)ACC systems, but it is very important to be aware of the differences in simulation results that can be found as a result of the simplifications to allow mesoscopic modelling.