Does unmarked on-street parking accommodate more cars—because smaller cars take less space? One would intuitively think so, but because of the mismatch effect of very small cars, unmarked spacing may not be more efficient. This study uses computer simulation where queues of randomly generated vehicles are assigned to marked and unmarked spaces. Simulation results show that unmarked parking is only more efficient when the curb is more segmented, or significantly different from the integer times of the optimal length of one marked space. Otherwise, marked parking or shorter marked parking under high demand is better. Unmarked parking also has higher requirement for considerate behavior. This simulation study also finds that vehicle downsizing only significantly improves parking efficiency when the vehicle is downsized to two-seaters that can vertically park. The study also proposes a new type of “block-based” parking that achieves some of the flexibility of unmarked parking while keeping mismatch-effect relatively low.