Online auction platforms like eBay provide a wide range of auctions containing substitutable goods. Some of these auctions exhibit parallel elements which mean that two or more auctions run side by side for a certain time. In this thesis I introduce an experimental setup of three sellers and four buyers in an ascending second price auction environment where every seller runs one auction with a homogeneous good and the buyers are confronted with single unit demand. For the special case of parallel multiple auctions, auctions ending at the same time, I find significantly lower efficiency due to coordination failure. In the following I present three auction design elements which could solve the coordination failure problem. First, auctions which starts and end with a delay also called overlapping multiple auctions. Second, parallel multiple auctions with stochastic deadlines. Third, I introduce an additional endogenous seller decision into the experimental environment. Particularly, the results of the overlapping multiple auctions and multiple auctions with endogenous seller decision show a reduction of the coordination failure. As a result I also find an increasing of the market efficiency for these two auction designs.