Rate-splitting multiple access (RSMA), space division multiple access (SDMA), and non-orthogonal multiple access (NOMA) have gained significant popularity and are extensively utilized across various domains. However, it is still unclear whether hybrid RSMA-SDMA-NOMA (HybridRDN) would seamlessly combine the advantages of RSMA, SDMA, and NOMA to contribute to the computation offloading of autonomous vehicle systems. To address the above issue, this paper introduces a novel HybridRDN-assisted computation offloading fleet (COF) scheme tailored for autonomous vehicle systems. First, we propose a stochastic-geometry-aided method to model the offloading framework. Afterwards, the task vehicles (TVs) ingeniously employ the proposed HybridRDN scheme to offload tasks to the resource vehicles (RVs) in each COF to relieve their computational burden. Diverging from the sole optimization of the task segmentation ratio or the transmission rate, a joint optimization problem involving the transmission weighting factor, the HybridRDN precoding matrix, the common rate, and the task segmentation ratio, is formulated, which aims to minimize the average delay of the COF system while approaching the rate performance of the ideal HybridRDN. Furthermore, a delay-optimal alternating optimization algorithm (DOAOA) is developed to obtain the solution for the optimization problem. Experimental results validate the plausibility and superiority of the proposed framework compared to the state-of-the-art schemes.