We present a simulation platform for access selection algorithms in heterogeneous wireless networks, called "ABCDecision". The simulator implements the different parts of an Always Best Connected (ABC) system, including Access Technology Selector (ATS), Radio Access Networks (RANs), and users. After describing the architecture of the simulator, we show an overview of the existing decision algorithms for access selection. Then we propose a new selection algorithm in heterogeneous networks and we run a set of simulations to evaluate the performance of the proposed algorithm in comparison with the existing ones. The performance results, in terms of the occupancy rate, show that our algorithm achieves a load balancing distribution between networks by taking into consideration the capacities of the available cells.